UPSC CISF-AC-EXE Archives

31. Which one of the following statements about carbon dioxide is not

Which one of the following statements about carbon dioxide is not correct?

[amp_mcq option1=”It is a basic oxide.” option2=”It is a greenhouse gas.” option3=”It forms dry ice.” option4=”It is consumed during photosynthesis.” correct=”option1″]

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The statement that carbon dioxide is a basic oxide is not correct.

Oxides of non-metals, like carbon dioxide (CO₂), are typically acidic oxides. When dissolved in water, CO₂ forms carbonic acid (H₂CO₃). Basic oxides are usually formed by metals.

Carbon dioxide is indeed a significant greenhouse gas, trapping heat in the atmosphere. Solid carbon dioxide is commonly known as dry ice. During photosynthesis, plants consume carbon dioxide from the atmosphere, along with water and sunlight, to produce glucose (sugar) and oxygen.

32. Which one of the following is a reducing substance?

Which one of the following is a reducing substance?

[amp_mcq option1=”Oxygen” option2=”Iron” option3=”Potassium permanganate” option4=”Potassium dichromate” correct=”option2″]

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Iron is a reducing substance.

A reducing substance (or reductant) is a species that loses electrons in a redox reaction, causing another substance to be reduced while itself being oxidized. Iron can readily lose electrons to form Fe²⁺ or Fe³⁺ ions, thus acting as a reducing agent.

Oxygen, Potassium permanganate (KMnO₄), and Potassium dichromate (K₂Cr₂O₇) are typically strong oxidizing agents, meaning they readily gain electrons from other substances, causing the other substance to be oxidized while they themselves are reduced.

33. Electron was discovered by

Electron was discovered by

[amp_mcq option1=”Michael Faraday” option2=”Joseph John Thomson” option3=”Henry Cavendish” option4=”Earnest Rutherford” correct=”option2″]

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The electron was discovered by Joseph John Thomson.

J.J. Thomson discovered the electron in 1897 through his experiments with cathode ray tubes, determining that cathode rays were composed of negatively charged particles much smaller than atoms.

Michael Faraday contributed significantly to electromagnetism and electrochemistry. Henry Cavendish discovered hydrogen and determined the composition of water. Ernest Rutherford conducted the gold foil experiment leading to the discovery of the atomic nucleus and later discovered the proton.

34. Which one of the following are the most widespread inorganic pelagic d

Which one of the following are the most widespread inorganic pelagic deposits on the ocean floor?

[amp_mcq option1=”Red clay” option2=”Radiolarian ooze” option3=”Volcanic dust” option4=”Calcareous ooze” correct=”option1″]

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Red clay is the most widespread inorganic pelagic deposit on the ocean floor.

Pelagic deposits are deep-sea sediments. Red clay is composed of fine-grained detrital material, volcanic ash, and cosmic dust, accumulating slowly in areas away from continental margins and where biogenic sedimentation is low, typically in the deepest ocean basins.

Radiolarian ooze and calcareous ooze are examples of biogenic pelagic deposits, formed from the remains of marine organisms. Volcanic dust can contribute to red clay but is not the deposit itself.

35. Match List I with List II and select the correct answer using the code

Match List I with List II and select the correct answer using the code given below the lists:
List I (Wildlife Sanctuaries)
List II (State)

A. Mahananda	1. Odisha
B. Malabar	2. Tamil Nadu
C. Satyamangalam	3. West Bengal
D. Lakhari Valley	4. Kerala

Code:

[amp_mcq option1=”1 2 4 3″ option2=”1 4 2 3″ option3=”3 4 2 1″ option4=”3 2 4 1″ correct=”option3″]

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The correct match is A-3, B-4, C-2, D-1.

Mahananda Wildlife Sanctuary is in West Bengal. Malabar Wildlife Sanctuary is in Kerala. Satyamangalam Wildlife Sanctuary is in Tamil Nadu. Lakhari Valley (or Lakhari Ghati) Wildlife Sanctuary is in Odisha.

Matching wildlife sanctuaries/national parks with their respective states is a common type of question in geography and environment sections of competitive exams. Knowing the locations of major protected areas is important.

36. The Headquarters of Central Railway Zone of Indian Railways is located

The Headquarters of Central Railway Zone of Indian Railways is located at

[amp_mcq option1=”Jabalpur” option2=”Mumbai” option3=”Secunderabad” option4=”Allahabad” correct=”option2″]

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The Headquarters of the Central Railway Zone of Indian Railways is located in Mumbai.

The headquarters is specifically located at the Chhatrapati Shivaji Maharaj Terminus (CSMT) in Mumbai.

Indian Railways is divided into several zones for administrative purposes. Other major railway zone headquarters include Kolkata (Eastern and South Eastern), Chennai (Southern), New Delhi (Northern), Secunderabad (South Central), and Jabalpur (West Central).

37. Which one among the following is the oldest nuclear power plant in

Which one among the following is the oldest nuclear power plant in India?

[amp_mcq option1=”Kaiga” option2=”Tarapur” option3=”Kundankulam” option4=”Kakrapar” correct=”option2″]

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The oldest nuclear power plant in India is the Tarapur Atomic Power Station (TAPS).

TAPS was the first commercial nuclear power station built in India, commissioned in 1969.

Kaiga Atomic Power Station is located in Karnataka. Kundankulam Nuclear Power Plant is located in Tamil Nadu and is currently the largest in India. Kakrapar Atomic Power Station is located in Gujarat.

38. The volcanic island ‘Barren Island’ is located in

The volcanic island ‘Barren Island’ is located in

[amp_mcq option1=”Chile” option2=”India” option3=”Italy” option4=”Iceland” correct=”option2″]

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The correct answer is B.

Barren Island is an island located in the Andaman Sea.
It is a volcanic island and contains the only confirmed active volcano in India.
It is part of the Union Territory of Andaman and Nicobar Islands, India.

Barren Island is located about 138 km northeast of Port Blair, the capital of the Andaman and Nicobar Islands. The volcano erupted recently in 2017.

39. What is the number of all possible positive integer values of ‘n’ for

What is the number of all possible positive integer values of ‘n’ for which n² + 96 is a perfect square ?

[amp_mcq option1=”2″ option2=”4″ option3=”5″ option4=”Infinite” correct=”option2″]

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The correct answer is B.

We are looking for positive integer values of ‘n’ such that n² + 96 is a perfect square.
Let n² + 96 = k², where k is an integer.
Since n is a positive integer, n² is positive, so k² must be greater than n². This implies k > n (assuming k is positive, which it must be since k² = n² + 96).
Rearranging the equation, we get k² – n² = 96.
This is a difference of squares, which can be factored as (k – n)(k + n) = 96.
Since k and n are integers, (k-n) and (k+n) must be integer factors of 96.
Also, (k+n) – (k-n) = 2n. Since n is an integer, 2n is an even integer. This means (k-n) and (k+n) must have the same parity. Since their product (96) is even, both factors must be even.
Furthermore, since n is positive, k+n > k-n. Also, k+n > 0 (as n>0 and k>n).

We need to find pairs of even factors (a, b) of 96 such that a * b = 96 and b > a.
The factors of 96 are 1, 2, 3, 4, 6, 8, 12, 16, 24, 32, 48, 96.
The even factors are 2, 4, 6, 8, 12, 16, 24, 32, 48, 96.
Pairs (a, b) where a and b are even, a*b=96, and b > a:
1. (2, 48) -> k – n = 2, k + n = 48. Adding gives 2k=50, k=25. Subtracting gives 2n=46, n=23. (n=23 is a positive integer)
2. (4, 24) -> k – n = 4, k + n = 24. Adding gives 2k=28, k=14. Subtracting gives 2n=20, n=10. (n=10 is a positive integer)
3. (6, 16) -> k – n = 6, k + n = 16. Adding gives 2k=22, k=11. Subtracting gives 2n=10, n=5. (n=5 is a positive integer)
4. (8, 12) -> k – n = 8, k + n = 12. Adding gives 2k=20, k=10. Subtracting gives 2n=4, n=2. (n=2 is a positive integer)
We found 4 distinct positive integer values for n: 23, 10, 5, and 2.
Therefore, there are 4 possible positive integer values of ‘n’ for which n² + 96 is a perfect square.

40. The sum of two positive integers is 52 and their LCM is 168. What is t

The sum of two positive integers is 52 and their LCM is 168. What is the ratio between the numbers?

[amp_mcq option1=”2:3″ option2=”5:4″ option3=”7:6″ option4=”7:8″ correct=”option3″]

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The correct answer is C.

Let the two positive integers be x and y.
Given: x + y = 52 and LCM(x, y) = 168.
Let g be the Greatest Common Divisor (GCD) of x and y. So, x = ga and y = gb, where a and b are coprime positive integers (gcd(a, b) = 1).
Using the given information:
1. x + y = ga + gb = g(a + b) = 52.
2. LCM(x, y) = g * a * b = 168.

From g(a + b) = 52, we know that g must be a divisor of 52. The divisors of 52 are 1, 2, 4, 13, 26, 52.
From gab = 168, we know that g must be a divisor of 168.
So, g must be a common divisor of 52 and 168.
Divisors of 52: 1, 2, 4, 13, 26, 52
Divisors of 168: 1, 2, 3, 4, 6, 7, 8, 12, 14, 21, 24, 28, 42, 56, 84, 168
Common divisors of 52 and 168 are 1, 2, 4. So g can be 1, 2, or 4.
We also have the constraints: a and b are positive integers and gcd(a, b) = 1.

Case 1: g = 1
a + b = 52/1 = 52
ab = 168/1 = 168
We look for two coprime numbers a and b such that a+b=52 and ab=168. This is equivalent to solving the quadratic equation t² – 52t + 168 = 0. The discriminant is 52² – 4*168 = 2704 – 672 = 2032, which is not a perfect square, so integer solutions for t (a, b) do not exist. Alternatively, list factor pairs of 168 and check sums: (1, 168) sum 169; (2, 84) sum 86; (3, 56) sum 59; (4, 42) sum 46; (6, 28) sum 34; (7, 24) sum 31; (8, 21) sum 29; (12, 14) sum 26. None sum to 52.

Case 2: g = 2
a + b = 52/2 = 26
ab = 168/2 = 84
We look for two coprime numbers a and b such that a+b=26 and ab=84. Factors of 84: (1, 84) sum 85, gcd 1 (valid); (2, 42) sum 44, gcd 2 (invalid); (3, 28) sum 31, gcd 1 (valid); (4, 21) sum 25, gcd 1 (valid); (6, 14) sum 20, gcd 2 (invalid); (7, 12) sum 19, gcd 1 (valid). None sum to 26.

Case 3: g = 4
a + b = 52/4 = 13
ab = 168/4 = 42
We look for two coprime numbers a and b such that a+b=13 and ab=42. Factors of 42: (1, 42) sum 43, gcd 1 (valid); (2, 21) sum 23, gcd 1 (valid); (3, 14) sum 17, gcd 1 (valid); (6, 7) sum 13, gcd 1 (valid).
The pair (6, 7) satisfies a+b=13 and gcd(6, 7)=1.
So, possible values for (a, b) are (6, 7) or (7, 6).
If (a, b) = (6, 7), then x = g*a = 4*6 = 24 and y = g*b = 4*7 = 28.
Check: 24 + 28 = 52. LCM(24, 28) = LCM(2³*3, 2²*7) = 2³*3*7 = 8*21 = 168. This is correct.
The two numbers are 24 and 28.
The ratio between the numbers is 24:28 or 28:24.
24:28 simplifies to 6:7 (dividing by 4).
28:24 simplifies to 7:6 (dividing by 4).
Option C is 7:6.

Therefore, the ratio between the numbers is 7:6 or 6:7. Option C provides 7:6.