`1.` You have to finish this work on time.
->This work.....must be done right away.....
`2.` Must the test be finished before ten?
->Must they.... finish the test before ten..
`3.` How long is it since they last saw that film?
-> When did... you last see the film?...
`4.` When was this car bought? (turn into active)
-> When ...did you buy this car?.....