46 .In nuclear raeactors the speed of neutrons is slowed down by -
47 .The phenomenon of radioactivity was discovered in 1898 A. D. by-
48 .Heavy metal got their name because compared to other atoms they have
49 .Chemical name of vitamin A is -
50 .Gas used for artificial ripening of fruits is:
51 .The process by which vegetable ghee is manufactured is known as-
52 .The Î± - particles are-
53 .Chemically vermillion is
54 .Which of the following is responsible for permanent hardness of water?
55 .Cid rain is due to
56 .Which is fight and flight organ?
57 .Rate of diffusion of a gas is -
58 .If a refrigerator's door is kept open, then-
59 .The gas used to extinguish fire is -
60 .The ultraviolet rays can be checked by -