Two particles separated at a horizontal distance X as shown in fig. they projected at the same line as shown in fig. with different initial speeds. The time after which the horizontal distance between them become zero

Question

https://clay6.com/mpaimg/pc47.jpg

( A ) None of these
( B ) $\frac{x}{u}$
( C ) $\frac{u}{2x}$
( D ) $\frac{2u}{x}$