21) The acid commonly present in lemon and grapefruit is:
(A) Lactic acid
(B) Citric acid
(C) Ascorbic acid
(D) Tartaric acid
22) The chemical name of laughing gas is:
(A) Nitric oxide
(B) Nitrogen dioxide
(C) Nitrogen pentoxide
(D) Nitrous oxide
23) Which of the following is the lightest substance known?
(A) Oxygen
(B) Nitrogen
(C) Hydrogen
(D) Carbon
24) Wood is the main raw material for the manufacture of:
(A) Gun powder
(B) Paint
(C) Ink
(D) Paper
25) A body immersed in a fluid experiences an upward thrust which depends on:
(A) The weight of the fluid displaced by it
(B) The volume of the body
(C) The mass of the body
(D) None of the above
26) In the microphone, used in the public address system:
(A) Sound waves are converted into electric signals which are amplified and transmitted
(B) Sound waves are directly transmitted
(C) Electric signals are first converted into sound waves
(D) Amplification is not required
27) Which of the following acids secreted internally, helps in digestion?
(A) Sulphuric
(B) Citric
(C) Hydrochloric
(D) Acetic
28) When water is heated from 0°C to 10°C the volume of water?
(A) Increase steadily
(B) Decrease steadily
(C) First increases, then decreases
(D) First decreases, then increases
29) The unit for measuring intensity of Noise is called:
(A) Knot
(B) Calorie
(C) Ohm
(D) Decibel
30) Calcium content is maximum in:
(A) Sorghum
(B) Pearl Millet
(C) Wheat
(D) Maize