Jane's the best tennis player ____ has been selected from that club.
The right answer is supposed to be c) that. However, I don't understand why "who" isn't used instead! Why?
Does that help?
Well ... thank you.
Hmmm... Maybe I shouldn't try to understand it, but simply learn it...
"A tennis player" (or the best one) is a person, not a thing, so I don't understand why "who" couldn't be used here, anyway, there are things that can't be understood (when learning a language)... For me, this is probably one of them.