---Tell us, Mark, what is the cause of the American Civil War?
---Well, is it _______the black slaves wanted freedom?
| A．how | B．why |
| C．because | D．when |
The earlier settlers learned to farm the land through ______ and error.
| A．test |
| B．trial |
| C．experiment |
| D．try |
The moment she heard of the news that her son was involved in the crime, she ______ pale.
| A．went |
| B．got |
| C．changed |
| D．appeared |
I didn't see you at the meeting. If you ______ , you would have met my brother.
| A．has come |
| B．did come |
| C．had come |
| D．came |
Don't use words and expressions or phrases ______ only to people with specific knowledge.
| A．being known |
| B．having known |
| C．to be known |
| D．known |
Emergency line operators must always ______ calm.
| A．grow |
| B．stay |
| C．appear |
| D．become |