They are not naughty in my class ten years ago.

A              B                                           C

The old man likes tell stories now.

                        A     B      C

It was the first day, little Tom went to school. When he came back home, his father asked him, "How many pupils did you find in your classroom, Tom?" "It's hard to say." Tom said, "There were thirty-one when the teacher was in the classroom, and there was none (没有人) when the teacher was out."