A particle is projected vertically upwards from a point A on the ground. It takes t1 time to reach a point B but it still continues to move up. If it takes further t2 time to reach the ground from point B then height of point B from the ground is
A. 1/2g(t1+t2)
B. gt1t2
C. 1/8g (t1+t2)²
D. ½ g t1 t2