Hi,
The teacher said, 'Have you done your homework?'
I have to convert it into indirect speech.
a) The teacher asked whether I had done my homework.
b)The teacher asked the boy whether he had done his homework.
c)The asked me whether I had done my homework.
Strictly speaking, I'd say The teacher asked the person whether he had done his homework. There's nothing in the direct speech to indicate that the teacher was talking to me, or to a boy. 'He' and 'his' can be used in the sense of both male and female here, to avoid saying 'he or she', 'his or her'.
Best wishes, Clive