Two spheres $A$ and $B$ of masses $m_1$ and $m_2$ respectively collide. $A$ is at rest initially and $B$ is moving with velocity $v$ along x-axis. After collision $B$ has a velocity $v/2$ in a direction perpendicular to the original direction. The mass $A$ moves after collision in the direction:

1. A
   $\theta ={\tan }^{-1}(-1/2)$ to the x-axis
2. B
   same as that of $B$
3. C
   opposite to that of $B$
4. D
   $\theta ={\tan }^{-1}(1/2)$ to the x-axis