Which sentence best expresses the main idea of paragraph 6?

A、According to his teacher, Sherry’s son sat at the back of the room, talking to his friends.;

B、Mrs. Stifter said that she didn’t move seniors, she flunked them.;

C、The fear of failure motivated Sherry’s son to do well in English.;

D、Sherry was at first nervous and confused to learn that her son might fail English.