We believe scientists will a way to solve the problem of air pollution.
| A．set off | B．put off |
| C．come up with | D．catch up with |
You had better _____ home at once . Don’t keep your mother _____ .
| A．to…wait | B．going…waiting |
| C．to go…to wait | D．go…waiting |
Remember ______ the book in time when you have finished _____ it .
| A．to return…reading | B．returning…reading |
| C．returning…to read | D．to return…to read |
It willabout half an hour to get to the zoo by bus.
| A．spend | B．take | C．pay | D．cost |
Tom, together with his parents the yard when I saw him.
| A．is cleaning | B．was cleaning |
| C．are cleaning | D．were cleaning |