When an object is shot from the bottom of a long smooth inclined plane kept at an angle $60^{\circ }$ with horizontal, it can travel a distance $x_1$ along the plane. But when the inclination is decreased to $30^{\circ }$ and the same object is shot with the same velocity, it can travel $x_2$ distance. Then $x_1:x_2$ will be:

1. A
   $1:2$
2. B
   $2:1$
3. C
   $1:\sqrt{3}$
4. D
   $\sqrt{3}:2$