A process is an orphan when it's parent terminated without calling wait().
And therefore this child whose parent terminated has no one to pass its exit status to.
Technically, the question doesn't tell us if P terminated with a wait() system call or not. So, data is insufficient, I think.
But generally parent processes do call wait(), so a god probabilistic guess would be — No, C doesn't become an orphan.
This topic is slightly detailed, I'd advise you to read Galvin (get a pdf of it online :P)