The two bodies of masses M and m (M > m) are allowed to fall from the same height if the air resistance for each be the same then which body will reach the earth quickly

The force acting on the body of mass M are its weight Mg acting vertically downward and air resistance F acting vertically upward.

$\therefore$  Acceleration of the body, $a=g-\frac{F}{M}$

Now M > m, therefore, the body with larger mass will have great acceleration and it will reach the ground first.