The motion of a particle moving with S.H.M. from an extremity to the other, constitutes A. Half an oscillation B. One full oscillation C. Two oscillations D. None of these

The correct answer is: B. One full oscillation.

A simple harmonic motion (SHM) is a periodic motion where the restoring force is directly proportional to the displacement. The motion of a particle moving with S.H.M. from an extremity to the other and back again constitutes one full oscillation.

Option A is incorrect because it only considers half of the motion. Option C is incorrect because it considers twice the motion. Option D is incorrect because it does not consider any of the options.