A: Mary couldn't come to the party. She was in hospital.
B: Oh, poor thing. What happened?
A: Nothing. She's a doctor.
A made a mistake. He should say: She was at the hospital
A: My mother is in the college today.
B: It's never too late to study.
A: Oh, no. She's a teacher there.
A: Jack is in prison.
B: What an interesting job!
A: I'm afraid you don't understand...
A: Liz will have to go to school tomorrow...
B: Do you have classes in the evening?
A: No, Liz is my aunt. She wants to speak to my teachers.