Ans: (d)
72.When a ball drops onto the floor it bounces. Why does it bounce? [CDS
   (a) Newton"s third law implies that for every action (drop) there is a reaction
   (b) The floor exerts a force on the ball during the impact
   (c) The floor is perfectly rigid
   (d) The floor heats up on impact
Ans: (b)
73.The lowest possible temperature is : [RRB TC 2003]
   (a) -273°C
   (b) 0°C
   (c) -300°C
   (d) 1°C
Ans: (a)
74.Which one among the following will you put into pure water in order to pass
   electric current through it ? [CDS 2011]
   (a) Kerosene
   (b) Mustard oil
   (c) Lemon juice
   (d) Sugar
Ans: (d)
75.The temperature of the body of a healthy man is : [Uttrakhand PCS (Pre)
   (a) 37°C
   (b) 37°F
   (c) 98.4°C
   (d) 98.4°K
Ans: (a)
76.A refracting telescope consists of : [NDA 2012]
   (a) one concave mirror and one convex lens
   (b) two convex lenses of equal focal length