3. Vietnamese students have fewer vacations than American ones.
=> American students.......
4. Was the story interesting?
=> The story......
5. Does everybody know him well?
=> He............
6. We spent five hours getting to London.
=> It took ..........
7. Our sources of energy will soon end if we don't try to save them.
=>Unless
8. They began studying English in 2004.
=>They .......