We decided to go to the cinema after work.
1) Did we decide to go to the cinema after work?
2) Did we decide to go to the cinema or to the theater after work?
3) We decided to go to the cinema after work, didn't we?
4) Where did we decide to go after work?
He has done his homework when his mother phoned him.
1) Has he done his homework when his mother phoned him?
2) Has he done his homework when his mother phoned or came him?
3) He has done his homework when his mother phoned him, hasn't he?
4) When has he done his homework?