The following have zero average value in a plane electromagnetic wave

The correct answer is Option (3) → both electric field and magnetic field

In a plane electromagnetic wave, the electric field (E) and magnetic field (B) vary sinusoidally with time.

The average value of a sinusoidal quantity (like sin or cos) over one complete cycle is zero.

Therefore, both electric field and magnetic field have zero average value.

Correct Option: both electric field and magnetic field