'Question about the subject' versus 'questions for the subject'.

[learning54]

Hi teachers,
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.

[bhaisahab]

Hi teachers,
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.

Use "about" or "on", not "for".

[konungursvia]

Unless the question is to be put to the "subject" in person.