They love each other very much.
1. Do they love each other very much?
2. Who love each other very much?
3. Do they love or hate each other very much?
4. They love each other very much, do not they?
Listen to one of them.
1. Do listen to one of them?
2. Who listen to one of them?
3. Do listen to one of them or talk to them?
4. Listen to one of them, do not they?