28. Be careful! The slightest spark（火花）could ______ the fireworks.
| A．set about | B．set off | C．set out | D．set up |
If there is a lot of work．I'm happy to just keep on until it is finished．
| A． | to do | B． | to be doing |
| C． | done | D． | doing |
To learn English well, we should find opportunities to hear Englishas much as we can．
| A． | speak | B． | speaking |
| C． | spoken | D． | to speak |
Due to the heavy rain and flooding，ten million people have been forced _________ their homes．
| A．leaving | B．to leave |
| C．to be left | D．being left |
If we have illegal immigrants _________ in，many local workers will lose their jobs．
| A．came | B．coming |
| C．to come | D．having come |
The director had her assistant ________ some hot dogs for the meeting．
| A．picked up | B．picks up |
| C．pick up | D．picking up |