1、Ted saw an alien yesterday（否定句）
Ted( didn't)(see )an alien yesterday.
2、When we got home it was raing（一般疑问句）
( Was)(it) raining when( you)got home?
3、The boy was riding a bike when the UFO londed.
(What)(was )the boy(riding )when the UFO(landed
4、John(was doing )[do]his lessons at 9;00 last night.
5、They( moved)[move]Paris last month.