The light is still on. They ___ to turn it off when they left the room.
| A．must forget | B．could have forgotten |
| C．may forget | D．must have forgotten |
We keep in touch ____ writing often.
| A．with | B．of | C．on | D．by |
Who is it up _____ decide whether to go or not?
| A．to to | B．for for | C．to for | D．for to |
____ that they are inexperienced, they have done a good job.
| A．Giving | B．To give | C．Given | D．If given |
Thank you for the trouble you have ____ to help me.
| A．paid | B．taken | C．had | D．asked |
I like swimming, while what my brother enjoys ____.
| A．cooking | B．to cook | C．is cooking | D．cook |