The pipes have oil or water inside them, which is heated and sent to the storage tank until ______ to produce electricity.
| A．needed | B．needing |
| C．to need | D．having needed |
---What do you think _____ an important part in their daily lives?
---Music.
| A．plays | B．takes | C．makes | D．act |
He seems to be doing nothing, but _____ he is just waiting for his chance.
| A．actually | B．gradually | C．frequently | D．certainly |
The boss requested that he _____ there to work.
| A．was sent | B．be sent |
| C．should send | D．would be sent |
You must ______ your papers before you hand them in.
| A．go down | B．go across | C．go out | D．go through |
Did you have any difficulty _____ his house?
| A．on finding | B．to finding |
| C．for finding | D．in finding |