B. a rocket uses only liquid fuels whereas a jet can use solid fuels as well.
           C. while a rocket carries its own oxygen supply a jet draws its air out of the atmosphere.
           D. a rocket can propel vehicles into outer space whereas a jet cannot.
       (a)   B, C and D are correct
       (b)   C and D are correct
       (c)   A and B are correct
       (d)   A, C and D are correct
Ans : (b)
231. In cold regions, where temperature may fall below 0° C, farmers fill their fields with water to protect their crops from damage
       (a) water is abundantly available in cold regions
       (b) water has high specific heat capacity
       (c) water has low specific heat capacity
       (d) plenty of water is absorbed by soil in cold regions
Ans : (b)
232. The minimum length of a plane mirror in which a person can see himself full length should be:
       (a) equal to the person"s height
       (b) slightly more than his height
       (c) nearly half his height
       (d) nearly one-fourth his height
Ans : (c)
233. Endoscope, used by doctors for examining the inside of a patient"s stomach, works on the principle of:
       (a) reflection of light
       (b) dispersion of light
       (c) refraction of light
       (d) total internal reflection of light
Ans : (d)
234. The phenomenon of mirage is due to:
       (a) increased absorption of light by air at higher temperature
       (b) change in refractive index of air with change in temperature
       (c) total internal reflection
       (d) decreased absorption of light by air at higher temperature
Ans : (c)
235. If the distance between the earth and the sun were twice what it is now, the gravitational force exerted on the earth by the sun would
     be :
       (a) twice as large as it is now
       (b) four times as large as it is now
       (c) half of what it is now
       (d) one-fourth of what it is now
Ans : (d)
236. The atmosphere exerts enormous pressure on us. But we do not feel it because:
       (a) we are used to it
       (b) our bones are very strong and can with stand this pressure
       (c) the surface area of our head is very small
       (d) our blood exerts a pressure slightly more than that of the atmosphere