The key answer of exercise 2

a)

1. they
2. you
3. we
4. they
5. we
6. they
7. you
8. we

b)

1. A: Are you students?; B: No, we aren’t. We're teachers.
2. A: Are they from France.; B: Yes, they are. They're from Paris.
3. A: Are you and Charlie brothers?; B: No, we aren’t. We're friends.
4. A: Are you a pilot?; B: No, I'm not. I’m an actor.
5. A: Are Jack and Diane English.; B: No, they aren’t. They’re American.
6. A: Is your car new?; B: No, it isn’t. It's old.