A simple pendulum has a hollow sphere containing  mercury suspended by means of a wire. If a little mercury is drained off. The period of the pendulum will

Time period  increases because effective length increased,when mercury is completely full , sphere with mercury center of gravity is sphere natural center, but when little mercury drains out, the center of gravity of mercury shifts to a point below natural center of sphere, hence length of the pendulum(l)  is increased , as Time period T α l, time period also increases