The time period of a pendulum is a function of its length only and does not depend on the mass of its bob. Mathematically, the time period of a pendulum can be written as:

`T = 2pi sqrt(L/g)`

where T is the time period of the pendulum, L is the pendulum length and g is the acceleration due to gravity. Hence, time period of a pendulum is independent of the mass of its bob.

Thus, if we increase the mass of the bob of a pendulum by a factor of 3, its time period will remain unchanged. Option **(b)** is correct.

On the other hand, if we changed the length of the pendulum by a factor of 3, say increased it by a factor of 3, its time period will increase by a factor of `sqrt (3)` .

Hope this helps.

**Further Reading**