A simple pendulum of length `l` is connected to the ceiling of a vehicle that is moving down along a smooth inclined plane `4` in `5`. Then its period of oscillation is
A. `2pi sqrt((5l)/(4g))`
B. `2pisqrt((4l)/(5g))`
C. `2pisqrt((5l)/(3g))`
D. `2pi sqrt((3l)/(5g))`