When we …(see) … them last night, they …(sing)… ; They …(say)… they …(sing)… since six o'clock

1. When we …(see) … them last night, they …(sing)… ; they …(say)… they …(sing)… since six o’clock.
2. We …(wait)… for you when you …(get)… back tomorrow.
3. They …(not come)… home until they …(see)… everything.
4. What do you think the children …(do)… when we get home ?
5. I’m sure the letter won’t arrive in time unless it …(send)… by air