(a) A p-n diode is said to be reverse biased if its $p$ side is at low potential with respect to $n$ side.
In option (a) $p$ side is at $- \ 6$ V while $n$ is at $\ –3$ V.
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.