Answer:
The correct answer is c) 100 m
Given:
The horizontal range of a projectile that is fixed at an angle to the horizontal plane $=15^{\circ}$
Range $=50 m$
In the first case range $=50= u ^{2} / g \left(\sin 2 \times 15^{\circ}\right)$
$50=\frac{2}{2 g }$
$\frac{ u ^{2}}{ g }=100$
In 2nd case range $=\frac{ u ^{2}}{ g \left(\sin 2 \times 45^{\circ}\right)}$
As we know $\sin 90^{\circ}=1\right)$
$=\frac{100}{1}\left
$=100 m$