UPSC NDA-1

21. Which one among the following statements about the Mansabdari system i

Which one among the following statements about the Mansabdari system is correct ?

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All army troopers were allotted mansabs.
Mansabs were usually assigned on the basis of ancestry.
Position and salary of mansabdars were indicated by a numerical designation called zat.
Mansabdars were never paid in cash.
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The correct answer is C) Position and salary of mansabdars were indicated by a numerical designation called zat.
In the Mughal Mansabdari system, ‘Zat’ was a numerical value that determined the Mansabdar’s personal status, rank, and personal pay. It was distinct from ‘Sawar’, which indicated the number of cavalrymen the Mansabdar was required to maintain.
The Mansabdari system was a grading system used by the Mughals to fix rank, salary, and military responsibilities. Mansabs were not usually assigned solely based on ancestry, although it might have played a role; merit and loyalty were also considered, and the system incorporated people from various backgrounds. Not all army troopers were Mansabdars; the rank was assigned to nobles, officials, and military commanders. While Mansabdars were often paid through revenue assignments (jagirs), they were sometimes paid in cash (‘naqd’), particularly in the early phase or for specific appointments.

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22. Freedom fighter Kanaklata Barua was martyred in :

Freedom fighter Kanaklata Barua was martyred in :

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Sepoy Mutiny
Quit India Movement
Non-Cooperation Movement
Peasant Uprising of 1893 - 1894
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The correct answer is B) Quit India Movement.
Kanaklata Barua was a prominent figure in the Indian independence movement from Assam. She participated in the Quit India Movement in 1942.
During the Quit India Movement, on 20th September 1942, a procession led by her marched towards the Gohpur police station in Assam to hoist the national flag. Kanaklata, who was leading the procession, was shot dead by the British police while holding the flag. She became a martyr and a symbol of courage for her sacrifice during the movement.

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23. Toothpaste prevents tooth decay by :

Toothpaste prevents tooth decay by :

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neutralizing the excess acidity.
means of emulsification.
the action of fluoride.
making a coat of calcium over the teeth surface.
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The correct answer is C) the action of fluoride.
The primary mechanism by which toothpaste prevents tooth decay is through the action of fluoride. Fluoride incorporated into toothpaste strengthens tooth enamel by promoting the formation of fluorapatite, a crystalline structure more resistant to acid dissolution than hydroxyapatite, the main component of enamel.
Fluoride also aids in the remineralization of early enamel lesions and inhibits the ability of plaque bacteria to produce acids. While toothpaste may also contain ingredients that help neutralize acids (Option A), fluoride is the key active ingredient specifically responsible for the significant reduction in dental caries incidence seen with the widespread use of fluoride toothpaste. Option B (emulsification) is unrelated to preventing decay. Option D (making a coat of calcium) is an inaccurate description of how toothpaste ingredients work.

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24. Among the following, which is not the correct method for keeping the

Among the following, which is not the correct method for keeping the curd ?

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Keeping in stainless steel vessel
Keeping in copper vessel
Keeping in plastic vessel
Keeping in glass vessel
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The correct answer is B) Keeping in copper vessel.
Curd is acidic due to the presence of lactic acid produced during fermentation. Acidic substances can react with certain metals, such as copper, to form potentially harmful salts.
Keeping acidic food like curd in copper vessels is not recommended because the acid can react with the copper metal. This reaction can leach copper ions into the food, potentially leading to health issues if consumed regularly in significant amounts. Stainless steel, plastic, and glass are non-reactive materials commonly used for storing acidic food items safely.

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25. An iron nail dipped in copper sulphate solution turns brown. This is d

An iron nail dipped in copper sulphate solution turns brown. This is due to which one of the following types of reactions ?

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Addition reaction
Decomposition reaction
Substitution reaction
Displacement reaction
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The correct answer is D) Displacement reaction.
This reaction involves a more reactive metal (iron, Fe) displacing a less reactive metal (copper, Cu) from its salt solution (copper sulphate, CuSO4). The general form of a displacement reaction involving metals is A + BX → AX + B, where A is more reactive than B.
The reaction is represented as: Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s). The iron nail gets coated with brown copper metal. This is a classic example illustrating the reactivity series of metals, where iron is higher than copper. It is also a redox reaction where iron is oxidized and copper ions are reduced. While substitution reactions also involve replacement, “displacement reaction” is the specific term used for this type of reaction involving elements and compounds.

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26. Which one of the following apparatus is used for separating benzene an

Which one of the following apparatus is used for separating benzene and water mixture ?

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Round bottom flask
Conical flask
Separating funnel
Dean and Stark apparatus
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The correct answer is C) Separating funnel.
A separating funnel is a piece of laboratory glassware used to separate immiscible liquids, i.e., liquids that do not mix and form distinct layers, based on their densities. Benzene and water are immiscible; benzene is less dense than water.
When a mixture of benzene and water is placed in a separating funnel, the two liquids separate into layers (water at the bottom, benzene at the top). The stopper is then opened, and the lower layer (water) is drained out through the stopcock until the interface between the two layers reaches the stopcock. The stopcock is then closed, and the upper layer (benzene) is collected in a separate container. Round bottom flasks and conical flasks are used for mixing, heating, or storage, not for separating immiscible liquids. A Dean and Stark apparatus is used for determining moisture content by distillation.

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27. Which of the hydrocarbons are arranged as per the increasing order of

Which of the hydrocarbons are arranged as per the increasing order of their boiling points ?

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Methane, Butane, Propane, Heptane
Propane, Butane, Pentane, Octane
Propane, Butane, Heptane, Methane
Octane, Ethane, Methane, Propane
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The correct answer is B) Propane, Butane, Pentane, Octane.
For a homologous series of hydrocarbons like alkanes, the boiling point generally increases with increasing molecular weight, which corresponds to an increasing number of carbon atoms. This is because larger molecules have stronger van der Waals forces (London dispersion forces), requiring more energy (higher temperature) to overcome them and transition from liquid to gas phase.
The number of carbon atoms in the given hydrocarbons are: Methane (C1), Ethane (C2), Propane (C3), Butane (C4), Pentane (C5), Heptane (C7), Octane (C8). Arranging them by increasing carbon number gives the expected order of increasing boiling points: C1 < C2 < C3 < C4 < C5 < C6 < C7 < C8. Option B lists hydrocarbons in the order: Propane (C3), Butane (C4), Pentane (C5), Octane (C8), which corresponds to increasing carbon numbers (3 < 4 < 5 < 8), and thus increasing boiling points.

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28. Browning of the chopped apple can be minimized by :

Browning of the chopped apple can be minimized by :

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using table sugar.
preserving in a container.
using lemon juice.
using milk of magnesia.
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The correct answer is C) using lemon juice.
Browning of chopped apples is caused by enzymatic oxidation, specifically the action of the enzyme polyphenol oxidase when exposed to oxygen. Lemon juice contains citric acid and ascorbic acid (Vitamin C). The acidity lowers the pH, which inhibits the enzyme’s activity, and ascorbic acid is an antioxidant that preferentially reacts with oxygen, preventing the oxidation of phenolic compounds.
Other methods to minimize browning include using other acidic solutions (like pineapple juice or vinegar), covering the apple surface to reduce oxygen exposure, or blanching (briefly heating) to denature the enzyme, although blanching can alter texture. Using milk of magnesia (a base) would increase the pH and likely promote enzymatic activity, worsening browning. Sugar might help reduce water activity but is not effective against enzymatic browning.

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29. Which one of the following structures or components is not always pr

Which one of the following structures or components is not always present in living cells ?

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Cell wall
Plasma membrane
Cytoplasm
Genetic material
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The correct answer is A) Cell wall.
While the plasma membrane, cytoplasm, and genetic material (DNA or RNA) are fundamental components found in *all* living cells (both prokaryotic and eukaryotic), the cell wall is not universally present.
A cell wall is a rigid outer layer found in plant cells, fungal cells, bacterial cells, and some protists. However, animal cells, which are also living cells, lack a cell wall. Therefore, the cell wall is not always present in living cells.

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30. One advantage of sexual reproduction over asexual reproduction is that

One advantage of sexual reproduction over asexual reproduction is that it helps species to survive over long evolutionary time. This is because sexual reproduction produces :

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more offspring in each reproductive cycle.
robust and healthy offspring.
genetically similar offspring.
more variation in offspring.
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The correct answer is D) more variation in offspring.
Sexual reproduction involves the fusion of gametes from two parents, leading to a combination of genetic material. This process, along with mechanisms like crossing over during meiosis, generates offspring with unique genetic combinations, increasing genetic variation within the population.
Genetic variation is crucial for the long-term survival of a species, especially in changing environments. A diverse gene pool increases the likelihood that some individuals will possess traits that allow them to adapt to new conditions, resist diseases, or survive environmental stresses, thereby ensuring the continuation of the species over evolutionary time. Asexual reproduction, while often faster and producing more numerous offspring in stable environments (countering option A), results in genetically similar offspring, making the population less adaptable to change.

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