A small bob attached to a light inextensible thread of length `l` has a periodic time `T` when
allowed to vibrate as a simple pendulum. The thread is now suspended from a fixed end `O` of a vertical rigid rod of length `(3l)/(4)` (as in figure). If now the pendulum performs periodic oscillations in this arrangement, the periodic time will be-
A. `(3T)/(4)`
B. `(T)/(2)`
C. `T`
D. `2T`
