dialogue: M: I think something is wrong with Mr. Hudson. He's not as cheerful as usual. W: I don't know what it could be. M: I heard last week that his mother had been ill. I wonder if that's the trouble. W: I doubt that. Yesterday he told me his mother felt much better. M: Maybe he has a problem here at work. W: I don't think that he has any problems with his job. It's well-known that Mr. Hudson is the best worker among us. M: Perhaps there is some trouble in his home. W: Well. The headmaster phoned this morning. M: That must be the problem. He's worried about his son.
question: Which may be the reason why Mr. Hudson is so sad?
choice: His mother's illness. Maybe his son has brought him some trouble. His manager wants to fire him.
answer: Maybe his son has brought him some trouble.