Today arose this question in one of my classes, and I don't know which one is better or if both are OK. For me is 'a', but I don't know why.
a) "I'm using 'who' because I'm asking a question about the subject".
b) "I'm using 'who' because I'm asking a question for the subject".
Thanks in advance.
Unless the question is to be put to the "subject" in person.