Starvation describes a situation where a thread (or a process) is unable to gain regular access to shared resources and is unable to make progress.
[Source : https://docs.oracle.com/javase/tutorial/essential/concurrency/starvelive.html ]
In the given question, $P2$ can't enter critical section (CS) unless $P1$ executes V(X) once. Thus, $P1$ stops progress of $P2$. (Even when $P2$ wants to execute CS it can't do so). So, $P2$ can starve until $P1$ starts execution.
After $P1$ executes V(X), it enters CS and now $P2$ which was initially blocked on P(X) can also enter CS. Now, in this situation when both processes are in CS, even if $P1$ has completed it's execution it can't exit CS until $P2$ exits once. It gets blocked at P(X) until $P2$ executes V(X). Thus, here $P2$ stops progress of $P1$ and so, $P1$ can starve until $P2$ exits the CS.
$\therefore$ Ans is $(a)$.