V

1.Riding a bike up the hill is really difficult to us.- It is really difficult for us to ride a bike up a hill.

2.Although he is young,he still manages to win the race.- In spite of being young, he still manages to win the race.

3. His father drove carelessly ,but now he didn't .- He used to drive carelessly.

4. Tom is working on a big project. - Tom is working on a big project, isn't he ?

5. The scientists are trying a new way to use sun power.-A new way to use sun power is being tried by the scientists.

6. Her behavior annoyed her teachers. -  Her teachers found her behavior annoying.