THE TEACHER ASKED THE / HIS STUDENTS IF / WHETHER THEY WERE TIRED...
32. The teacher asked the / his students if / whether they were tired of their studies.
Or: The teacher asked if / whether the / his students were tired of their studies.
32. The teacher asked the / his students if / whether they were tired of their studies.
Or: The teacher asked if / whether the / his students were tired of their studies.