A)
1. The teacher said that she was going to explain a new grammar rule that day.
2. My parents said that they didn't see anything bad in wearing a uniform.
3. The children said that they would do their best to pass their exams successfully.
B)
1. Marry asked her classmate if she gained much by attending her elective courses.
2. The head teacher asked the students what subject they had chosen to take exams in.
3. Jack asked his new friend what dress code he had followed the previous year.
C)
1. The psychologist advised to start revising for exams as early as possible.
2. The professor warned not to cheat during the test.
3. One of the parents recommended to invite the primary school teacher to the school leavers' ball.