Act of swinging back and forth.

• A. Rotation
• B. Oscillation
• C. Vibration
• D. Pendulum

Answer: (B)

Oscillation describes motion that repeats in a regular cycle around an equilibrium position. When something swings, it moves away from the center, crosses the middle, reaches the opposite side, and then returns, repeating this pattern. This back-and-forth motion fits the idea of oscillation perfectly.

Rotation would be spinning around an axis in a circular path, not the back-and-forth along a line. Vibration is typically rapid, small-scale motion around an equilibrium and often at higher frequency, which isn’t the same as a deliberate swing. A pendulum is a specific setup that demonstrates oscillation, so naming the action emphasizes the motion itself rather than the particular object. Therefore, the act of swinging back and forth is oscillation.