UPSC CDS-2

41. Who among the following has won the Singles Title in Wimbledon Tennis

Who among the following has won the Singles Title in Wimbledon Tennis Championship (Women) in the year 2019?

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Karolina Pliskova
Simona Halep
Serena Williams
Naomi Osaka
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Simona Halep of Romania won the Wimbledon Women’s Singles title in 2019. She defeated Serena Williams in the final.
This question refers to a specific sports event winner from 2019.
Serena Williams was the runner-up. Karolina Pliskova and Naomi Osaka are also prominent tennis players, but they did not win the 2019 Wimbledon Women’s Singles title.

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42. Which one of the following is a decommissioned aircraft carrier?

Which one of the following is a decommissioned aircraft carrier?

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INS Rajput
INS Chakra
INS Khanderi
INS Viraat
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INS Viraat was an aircraft carrier of the Indian Navy. It was originally HMS Hermes of the Royal Navy and was acquired by India in 1987. It was decommissioned from service on March 6, 2017.
Decommissioned means the ship has been retired from active service.
INS Rajput was a guided-missile destroyer (decommissioned in 2021). INS Chakra refers to nuclear submarines leased from Russia. INS Khanderi is a Kalvari-class submarine commissioned in 2019.

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43. Lead nitrate on heating gives

Lead nitrate on heating gives

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PbO₂ and NO₂
PbO and NO₂
PbO and NO
PbO₂ and NO
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Heating lead nitrate (Pb(NO₃)₂) causes thermal decomposition, producing lead(II) oxide (PbO), nitrogen dioxide (NO₂), and oxygen (O₂).
The balanced chemical equation for the thermal decomposition of lead nitrate is: 2 Pb(NO₃)₂(s) → 2 PbO(s) + 4 NO₂(g) + O₂(g). Nitrogen dioxide is a reddish-brown gas, and this decomposition is often demonstrated to show its production.
The specific oxide formed depends on the metal and the temperature of decomposition. For lead nitrate, the primary solid product is lead(II) oxide (PbO). Lead(IV) oxide (PbO₂) is not formed under these conditions as a primary product of lead nitrate decomposition.

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44. The valency of phosphorus is

The valency of phosphorus is

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2, 3
3, 4
4, 5
3, 5
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Phosphorus commonly exhibits valencies of 3 and 5.
Phosphorus is in Group 15 (VA). In compounds like PH₃ or PCl₃, phosphorus has a valency of 3, using its three unpaired p-electrons for bonding. Due to the presence of vacant d-orbitals, phosphorus can expand its valence shell and form five covalent bonds, as seen in compounds like PCl₅ or P₂O₅, where its valency is 5.
Phosphorus can also exhibit other oxidation states and valencies in specific compounds, but 3 and 5 are the most common valencies.

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45. Which one of the following does not form oxide on reaction with

Which one of the following does not form oxide on reaction with oxygen?

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Magnesium
Lead
Tin
Silver
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Silver (Ag) is a noble metal and is relatively unreactive. While many metals readily react with oxygen to form oxides, silver does not easily form an oxide when exposed to oxygen in the air under normal conditions.
Reactivity with oxygen varies among metals. Highly reactive metals like Magnesium react readily, forming stable oxides. Lead and Tin are less reactive than Magnesium but still form oxides. Silver is one of the least reactive metals and does not readily oxidize.
Silver tarnishes when exposed to sulfur compounds in the air, forming silver sulfide (Ag₂S), which appears as a black layer. Direct reaction with oxygen to form silver oxide (Ag₂O) requires specific conditions, such as heating at lower temperatures (around 160-200°C) and the oxide decomposes at higher temperatures.

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46. Which one of the following is used for storing biological tissues?

Which one of the following is used for storing biological tissues?

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Liquid nitrogen
Liquid helium
Liquid argon
Liquid bromine
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Liquid nitrogen is commonly used for cryopreservation, which is the process of preserving biological tissues, cells, and organs at very low temperatures.
Liquid nitrogen boils at -196°C (-320°F). This extremely low temperature effectively halts biological activity, including enzymatic reactions and cellular degradation, allowing long-term storage of samples such as sperm, eggs, embryos, blood cells, tissue biopsies, and even whole organs for transplantation in some cases.
Liquid helium boils at an even lower temperature (-269°C) but is more expensive and typically used for specialized scientific applications like cooling superconducting magnets. Liquid argon (-186°C) has some industrial uses but is not standard for biological cryopreservation. Bromine is a liquid at room temperature and is highly toxic and corrosive, not suitable for storage.

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47. The radioactive isotope of hydrogen is

The radioactive isotope of hydrogen is

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protium
deuterium
tritium
hydronium
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Tritium (³H) is the radioactive isotope of hydrogen. It contains one proton and two neutrons.
Hydrogen has three naturally occurring isotopes: Protium (¹H, 1 proton, 0 neutrons), Deuterium (²H or D, 1 proton, 1 neutron), and Tritium (³H or T, 1 proton, 2 neutrons). Protium and Deuterium are stable isotopes.
Tritium is a beta emitter with a relatively short half-life of approximately 12.3 years. Hydronium (H₃O⁺) is a polyatomic cation formed when a proton (H⁺) is added to a water molecule (H₂O); it is not an isotope of hydrogen.

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48. Antibiotic such as penicillin blocks

Antibiotic such as penicillin blocks

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cell wall formation in bacteria
RNA synthesis in bacteria
DNA synthesis in bacteria
division in bacteria
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Antibiotics such as penicillin work by interfering with the synthesis of the bacterial cell wall, specifically the peptidoglycan layer.
Penicillin inhibits the transpeptidase enzymes (also known as penicillin-binding proteins or PBPs) that cross-link the peptidoglycan chains, which are essential for the structural integrity of the bacterial cell wall. This weakens the wall, leading to cell lysis (bursting) due to osmotic pressure.
Different classes of antibiotics target different processes in bacteria, such as protein synthesis (e.g., tetracyclines, erythromycin), DNA synthesis (e.g., quinolones), RNA synthesis (e.g., rifampicin), or metabolic pathways (e.g., sulfonamides).

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49. In human beings, the chromosomes that determine birth of a normal fema

In human beings, the chromosomes that determine birth of a normal female child are

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one X chromosome from mother and one X chromosome from father
one X chromosome from mother and one Y chromosome from father
two X chromosomes from mother and one X chromosome from father
one X chromosome and one Y chromosome from father and one X chromosome from mother
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In humans, sex is determined by the sex chromosomes. Females have two X chromosomes (XX), and males have one X and one Y chromosome (XY). A female child inherits one X chromosome from her mother (who can only contribute an X) and one X chromosome from her father (who can contribute either an X or a Y).
The mother’s gametes (ova) always carry an X chromosome. The father’s gametes (sperm) carry either an X or a Y chromosome. Fertilization with an X-carrying sperm results in an XX zygote (female), while fertilization with a Y-carrying sperm results in an XY zygote (male).
The father determines the sex of the child based on whether the sperm contributing to fertilization carries an X or a Y chromosome.

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50. Mature sclerenchyma cells have

Mature sclerenchyma cells have

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cellulose wall and are living
lignified wall and are living
suberized wall and are dead
lignified wall and are dead
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Mature sclerenchyma cells are characterized by having thick, lignified secondary cell walls and being dead at functional maturity.
Sclerenchyma provides mechanical support to the plant. The lignified walls make them rigid and strong. The two main types of sclerenchyma cells are fibres and sclereids.
Parenchyma and collenchyma cells are living at maturity and typically have cellulose walls. Collenchyma walls may be thickened but usually lack lignin. Suberized walls are found in cork cells (phellem).

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