UPSC CDS 2021 Answer Key

UPSC CDS 1 Exam 2021 General Knowledge Paper (Official Answer Key)

21. Which one of the following elements is a non-metal but is lustrous ?
(a) Carbon
(b) Silicon
(c) Germanium
(d) Iodine

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Answer – (D)

22. Which one of the following metals has both malleability and ductility properties ?
(a) Na
(b) Au
(c) Ce
(d) Hg

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Answer – (B)

23. We are given three copper wires of different lengths and different areas of cross-section. Which one of the following would have highest resistivity ?
(a) Copper wire of 50 cm length and 1 mm diameter
(b) Copper wire of 25 cm length and 0.5 mm diameter
(c) Copper wire of 10 cm length and 2.0 mm diameter
(d) All the wires would have same resistivity

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Answer – (D)

24. Which of the following statements about ‘fission’ is correct ?
1. It is related with the creation of new individuals by means of cell division in unicellular organism.
2. It is related with the transformation of heavier nuclei into smaller nuclei.
3. It is related with the creation of a heavier nuclei by means of combining two higher nuclei.
Select the correct answer using the code given below :
(a) 1 only
(b) 2 only
(c) 1 and 2 only
(d) 1 and 3 only

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Answer – (C)

25. Which one of the following is an electric conductor ?
(a) A plastic sheet
(b) Distilled water
(c) Human body
(d) A wooden thin sheet

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Answer – (C)

26. A non-spherical shining spoon can generally be considered as a
(a) Spherical mirror
(b) Parabolic mirror
(c) Plane mirror
(d) Lens

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Answer – (B)

27. Who amongst the following is a pione discovering the heating effect of electric current ?
(a) Isaac Newton
(b) Galileo Galilei
(c) James P. Joule
(d) J.J. Thomson

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Answer – (C)

28. Which one of the following laws of electromagnetism does not give the direction of magnetic field ?
(a) Right-hand thumb rule
(b) Fleming’s left-hand rule
(c) Fleming’s right-hand rule
(d) Faraday’s law of electromagnetic induction

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Answer – (D)

29. An antibiotic is not useful against a virus whereas a vaccine is. Which one of the following is the most appropriate reason for this?
(a) An antibiotic can break RNA only, whereas virus has DNA.
(b) An antibiotic is a carbohydrate in its chemical nature, whereas a vaccine is a protein which works well to kill a virus.
(c) Only a vaccine can break the genetic material of a virus.
(d) A virus does not use biochemical pathways which can be blocked by an antibiotic. But a vaccine can boost an immune system to fight the virus.

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Answer – (D)

30. ‘Sleeping sickness’ is caused by
(a) Trypanosoma
(b) Leishmania
(c) Plasmodium
(d) Paramecium

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Answer – (A)

31. Which one among the following is a free living animal ?
(a) Liver fluke
(b) Wuchereria
(c) Plasmodium
(d) Planaria

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Answer – (D)

32. Which one of the following is the structure of a cardiac muscle cell ?
(a) Cylindrical, Unbranched and Multinucleate
(b) Spinal shaped, Unbranched and Uninucleate
(c) Spinal shaped, Branched and Uninucleate
(d) Cylindrical, Branched and Uninucleate

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Answer – (D)

33. Which one of the following naturally occurring acids is found in abundance in tomato ?
(a) Acetic acid
(b) Citric acid
(c) Oxalic acid
(d) Tartaric acid

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Answer – (C)

34. Which one of the following is used in soda-acid fire extinguishers ?
(a) Sodium chloride
(b) Sodium hydrogen carbonate
(c) Calcium hydroxide
(d) Acetic acid

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Answer – (B)

35. Which one of the following sodium compounds is used for softening hard water ?
(a) Na2CO3
(b) NaHCO3
(c) NaOH
(d) Na2S04

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Answer – (A)

36. Calcium oxide reacts vigorously with water to produce slaked lime whose solution is used for white-washing walls. This slaked lime reacts with component (A) in air to form a thin layer of component (B) to give a shiny finish. What are the components (A) and (B)?
(a) A – O2; B – CaCO3
(b) A – CO2; B – Ca(OH)2
(c) A – O2; B – Ca(OH)2
(d) A – CO2; B – CaCO3

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Answer – (D)

37. How many internal reflections of light take place in the formation of primary rainbow?
(a) 0
(b) 1
(c) 2
(d) More than 2

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Answer – (B)

38. The direction of acceleration circular motion is along the in uniform
(a) direction of motion.
(b) tangent to the circle at the point of observation.
(c) direction of velocity.
(d) direction perpendicular to velocity.

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Answer – (D)

39. The weight of an object is due to
(a) the net force acting on it.
(b) the total of all forces acting on it irrespective of their directions.
(c) the force that it exerts on the ground.
(d) its inert property.

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Answer – (C)

40. The size of particles being studied in ‘nano-technology’ is about
(a) 1 Å – 10 n m
(b) 1 – 100 nm
(c) 1 – 50 μ
(d) 1 mm – 10 mm>

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Answer – (B)

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