UPSC NDA-2

41. The Panama Canal opened in 1914, links

The Panama Canal opened in 1914, links

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Red Sea and Mediterranean Sea
Atlantic Ocean and Pacific Ocean
Indian Ocean and Pacific Ocean
Adriatic Sea and Black Sea
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The Panama Canal is an artificial 82 km (51 mile) waterway in Panama that connects the Atlantic Ocean with the Pacific Ocean. It is a key conduit for international maritime trade.
– Panama Canal: Links the Atlantic Ocean (via the Caribbean Sea) and the Pacific Ocean.
– Suez Canal: Links the Mediterranean Sea and the Red Sea.
– Strait of Malacca: A major shipping lane linking the Indian Ocean and the Pacific Ocean (via the South China Sea).
Construction of the Panama Canal by the United States began in 1904 and it officially opened on August 15, 1914. It significantly reduced the time and distance required for ships to travel between the two great oceans, eliminating the need to navigate around the southern tip of South America (Cape Horn).

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42. Which one of the following statements is correct about effects of anti

Which one of the following statements is correct about effects of antibiotics on viruses ?

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Viruses are "non-living" entities but it can interact with antibiotics
Taking antibiotics cures viral infections
Viruses do not possess metabolic pathways on which antibiotics can function, whereas bacteria have such pathways
Viruses are resistant to antibiotics
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Antibiotics are designed to target specific structures or metabolic processes in bacteria, such as cell wall synthesis, protein synthesis (ribosomes), DNA replication, or specific enzymatic pathways. Viruses, being intracellular parasites, lack their own metabolic machinery; they hijack the host cell’s machinery for replication. Therefore, viruses do not possess the metabolic pathways or structures that antibiotics are designed to inhibit, rendering antibiotics ineffective against them.
– Antibiotics target bacterial processes, not viral ones.
– Viruses lack their own metabolic pathways for functions like replication, using host cell machinery instead.
– Taking antibiotics for viral infections is ineffective and contributes to antibiotic resistance in bacteria.
– Viral infections require antiviral medications, not antibiotics.
The misuse of antibiotics for viral infections is a major driver of antibiotic resistance, a growing global health crisis. Antiviral drugs work by targeting different stages of the viral life cycle, such as entry into the host cell, replication of viral genetic material, or assembly and release of new viruses. Examples of viral infections include the common cold, flu, COVID-19, measles, and HIV.

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43. Which one of the following terms describes the practice of growing two

Which one of the following terms describes the practice of growing two or more crops simultaneously on the same piece of land ?

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Crop rotation
Mixed cropping
Intercropping
Mixed farming
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Mixed cropping is the practice of growing two or more crops simultaneously on the same piece of land. The objective is often to minimize the risk of crop failure and improve soil fertility. Intercropping is a method of mixed cropping where crops are grown in definite row patterns. Since the question asks for the general term describing the practice of growing multiple crops *simultaneously* without specifying a pattern, mixed cropping is the most appropriate answer.
– Mixed cropping: Growing two or more crops simultaneously on the same land without a definite pattern.
– Intercropping: A type of mixed cropping where crops are grown in specific row arrangements.
– Crop rotation: Growing different crops on the same field in a planned sequence over different seasons or years.
– Mixed farming: A system of farming that combines crop production with the rearing of livestock.
Mixed cropping can provide benefits such as increased yield stability, reduced pest and disease incidence, improved soil health, and better utilization of resources (light, water, nutrients). Examples include growing wheat and gram together, or groundnut and sunflower. Intercropping, with its planned spatial arrangement, allows for easier management operations like harvesting and spraying.

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44. Which one of the following cell organelles may play a role in expellin

Which one of the following cell organelles may play a role in expelling excess water and wastes in case of unicellular organisms ?

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Lysosome
Vacuole
Golgi body
Endoplasmic reticulum
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In many freshwater unicellular organisms like *Paramecium* or *Amoeba*, contractile vacuoles are specialized organelles that collect excess water that enters the cell by osmosis and periodically expel it out. This process is crucial for osmoregulation, preventing the cell from bursting in a hypotonic environment. Wastes can also be expelled via this mechanism or through other means like diffusion or exocytosis.
– Vacuoles in unicellular organisms can include contractile vacuoles, which are vital for maintaining osmotic balance by expelling excess water.
– Lysosomes are involved in intracellular digestion.
– Golgi body (or Golgi apparatus) is involved in modifying, sorting, and packaging proteins and lipids for secretion or delivery to other organelles.
– Endoplasmic reticulum is involved in protein and lipid synthesis.
Contractile vacuoles are found mainly in protists living in freshwater habitats. Their rate of pulsation is regulated by the osmotic potential of the surrounding medium; they pump faster in more dilute environments. While primarily for water expulsion, they also contribute to the removal of some metabolic wastes.

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45. Which one of the following element’s isotope is used in the treatment

Which one of the following element’s isotope is used in the treatment of cancer ?

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Uranium
Cobalt
Sodium
Iodine
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Cobalt-60 is a widely used radioactive isotope in cancer treatment, specifically in external beam radiotherapy (using a Cobalt therapy machine) due to its emission of high-energy gamma rays which are effective in killing cancer cells.
– Radioisotopes like Cobalt-60 are used in cancer treatment (radiotherapy) to damage the DNA of cancer cells and prevent them from growing and dividing.
– Iodine-131 is used specifically in the treatment of thyroid cancer and hyperthyroidism.
– Uranium is primarily known for its use in nuclear power and weapons, not medical treatment in this context.
– Sodium isotopes are often used as tracers but not standard therapeutic agents for cancer.
Apart from Cobalt-60 and Iodine-131, other radioisotopes used in cancer treatment include Iridium-192 (brachytherapy), Cesium-137 (brachytherapy), Gold-198 (brachytherapy), and Phosphorus-32 (for certain blood disorders affecting bone marrow). Brachytherapy involves placing the radioactive source directly inside or next to the tumour.

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46. Atomic mass of an element is equal to the sum of number of

Atomic mass of an element is equal to the sum of number of

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electrons and protons only
protons and neutrons only
electrons and neutrons only
electrons, protons and neutrons
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The correct answer is (B) protons and neutrons only. The atomic mass of an element (more accurately, the mass number of a specific isotope or the relative atomic mass) is primarily determined by the mass of the particles in the nucleus. Protons and neutrons are located in the nucleus and account for almost all of an atom’s mass. The mass of electrons is negligible in comparison.
The nucleus of an atom contains protons and neutrons, which contribute significantly to its mass. Electrons have very little mass.
The Mass Number (A) of an isotope is the sum of the number of protons (Z) and neutrons (N) in its nucleus (A = Z + N). The atomic mass listed on the periodic table for an element is the weighted average of the masses of its naturally occurring isotopes, taking into account their relative abundances.

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47. Neutrons were discovered by

Neutrons were discovered by

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James Chadwick
Ernest Rutherford
J. J. Thomson
John Dalton
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The correct answer is (A) James Chadwick. James Chadwick discovered the neutron in 1932.
The discovery of the neutron completed the basic understanding of the composition of the atomic nucleus, alongside protons.
J. J. Thomson discovered the electron in 1897. Ernest Rutherford, through the gold foil experiment, discovered the atomic nucleus and later identified protons within the nucleus (in 1917-1919). John Dalton is credited with developing the modern atomic theory in the early 19th century.

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48. Which one of the following is the most fundamental characteristic of a

Which one of the following is the most fundamental characteristic of an element ?

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Melting point
Atomic number
Colour
Atomic weight
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The correct answer is (B) Atomic number. The atomic number (Z) of an element is defined as the number of protons in the nucleus of an atom of that element. This number is unique to each element and determines its fundamental chemical identity.
The atomic number is the defining characteristic of an element, determining its position in the periodic table and its chemical properties.
Melting point and color are physical properties that can vary depending on conditions or even within different forms (allotropes) of the same element. Atomic weight (more precisely, relative atomic mass) is the weighted average mass of isotopes of an element and is determined by the number of protons and neutrons, but the identity is fixed by the number of protons alone.

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49. How many covalent bonds are present in a Chloropropane molecule having

How many covalent bonds are present in a Chloropropane molecule having molecular formula, C₃H₇Cl ?

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6
8
9
10
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The correct answer is (D) 10. The molecular formula is C₃H₇Cl. This represents a chloropropane molecule, which is derived from propane (C₃H₈) by replacing one hydrogen atom with a chlorine atom. Let’s consider the structure of propan-1-ol (CH₃-CH₂-CH₂-Cl) or propan-2-ol (CH₃-CHCl-CH₃). Counting the single covalent bonds:
In CH₃-CH₂-CH₂-Cl:
C1-H (3 bonds)
C1-C2 (1 bond)
C2-H (2 bonds)
C2-C3 (1 bond)
C3-H (2 bonds)
C3-Cl (1 bond)
Total = 3 + 1 + 2 + 1 + 2 + 1 = 10 covalent bonds.
In CH₃-CHCl-CH₃:
C1-H (3 bonds)
C1-C2 (1 bond)
C2-H (1 bond)
C2-Cl (1 bond)
C2-C3 (1 bond)
C3-H (3 bonds)
Total = 3 + 1 + 1 + 1 + 1 + 3 = 10 covalent bonds.
A covalent bond is formed by the sharing of electron pairs between atoms. To find the total number of covalent bonds in a simple organic molecule, you need to count all the single, double, and triple bonds between atoms.
In organic molecules, carbon typically forms 4 bonds, hydrogen forms 1 bond, and chlorine forms 1 bond. By drawing the skeletal structure and adding hydrogens to satisfy valency, one can systematically count the bonds.

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50. Which one of the following statements is NOT correct ?

Which one of the following statements is NOT correct ?

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Buckminsterfullerene is an allotrope of carbon
Diamond is a good conductor of electricity
Graphite is a good conductor of electricity
In graphite, each carbon atom is linked to three other carbon atoms
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The statement which is NOT correct is (B) Diamond is a good conductor of electricity. Diamond has a structure where each carbon atom is bonded to four other carbon atoms via strong covalent bonds. All valence electrons are tightly held in these bonds, meaning there are no free electrons to carry charge. Therefore, diamond is a poor conductor of electricity (a good electrical insulator).
Electrical conductivity in materials depends on the presence of free charge carriers, such as free electrons. The arrangement and bonding of atoms determine the availability of these carriers.
Statement (A) is correct: Buckminsterfullerene (C60) is a form of carbon, belonging to the fullerene family, which are allotropes of carbon. Statement (C) is correct: Graphite conducts electricity because each carbon atom is bonded to three others, leaving one delocalized electron per atom that can move throughout the layers. Statement (D) is correct: In graphite, carbon atoms are arranged in hexagonal layers where each carbon is covalently bonded to three other carbon atoms.

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