Taking X and Y direction as shown
$u_{Ax}=60 \cos 30 ^{\circ}$
$\qquad= 30 \sqrt 3 m/s$
$u_{Ay}=60 \sin 30=30 m/s $
$u_{Bx}=-50 \cos \alpha$
$u_{By}=50 \sin \alpha $
A and B reach the same height at same time condition for collision
$u_{Ay}=u_{By}$
$30=50 \sin \alpha$
$\alpha =\sin ^{-1} \bigg(\large\frac{3}{5}\bigg)$
Hence d is the correct answer.