Pollution is a serious problem. Scientists have _____ some good ways to save it.
| A．come up with | B．come on | C．come out | D．come up |
________ fathers are both doctors.
| A．Jim's and Bob's | B．Jim's and Bob |
| C．Jim and Bob's | D．Jim and Bob |
Please __________ the light when you leave the classroom.
| A．turn on | B．turn up | C．turn off | D．turn down |
When you go _________ the street, you must be careful.
| A．crossing | B．cross | C．across | D．pass |
I ______ an hour finishing my homework yesterday.
| A．cost | B．paid | C．spent | D．took |
The shoes are beautiful. Please ___________
| A．try it on | B．try on it | C．try them on | D．try on them |