Explanation

(c) Horizontal distance of target is 200 m.
$Speed\ of\ bullet = 2000\ {ms}^{- 1}$
Time taken by bullet to cover the horizontal distance
$t = \frac{200}{2000} = \frac{1}{10}s$
During $\frac{1}{10}\ s,\ t$he bullet will fall down vertically due to gravitational acceleration.
Therefore, height above the target, so that the bullet hits the target is
$h = u + \frac{1}{2}gt^{2} = \left( 0 \times \frac{1}{10} \right) + \frac{1}{2} \times 10 \times (0.1)^{2}$
$= 0.05m = 5cm$