$A$ body is projected vertically upwards. The times corresponding to a specific height while ascending and while descending are $t_{1}$ and $t_{2}$ respectively. Then the velocity of projection is (where $g$ is acceleration due to gravity).

• A
  $g \sqrt{t_{1} t_{2}}$
• B
  $\frac{g t_{1} t_{2}}{t_{1}+t_{2}}$
• C
  $\frac{g \sqrt{t_{1} t_{2}}}{2}$
• D
  $\frac{g(t_{1}+t_{2})}{2}$