Choose the correct statements.

Periodic motion is a motion that repeats itself after equal intervals of time. It need not be oscillatory. For example, uniform circular motion is periodic but not oscillatory.

Oscillatory motion is a to and fro motion about a mean position. It need not be periodic. For example, in damped harmonic motion, the amplitude decreases with time, so the motion does not repeat exactly and is not strictly periodic.

Simple harmonic motion (SHM) is a special case of oscillatory motion where the restoring force is directly proportional to the displacement from the mean position. It is always to and fro (oscillatory) and repeats after equal intervals of time (periodic).

Therefore, simple harmonic motion is always oscillatory and always periodic.