In the circuit shown how will the glow of bulbs A and C be affected when the key k is switched on?

Brightness of A increases but that of C decreases

The correct answer is Option (3) → Brightness of A increases but that of C decreases

Brightness of C decreases because when switch is closed the current gets divided at the parallel junction.

Brightness at A increases because the net resistance by B and C is much less than C alone and thus the potential across A is increased.