1. You forgot to turn of the TV last night, didn't you ?

=> You didn't remember turn of the TV last night, did you ?

2. I think you should go to work by bike

=> Why don't you go to work by bike ?

3. We will plant more trees along this street

=> More tress will be planted along this street.

4. Is pollution the most serious problem ?

=> Pollution is the most serious problem, isn't it ?

5. Mr. Long lived in the country when he was a child
=> Mr. Long used to live in the country when he was a child.