We should study the new traffic rules and 1earn how___________ ourselves．
| A．protect | B．to protect | C．protecting | D．protected |
They stayed in Beijing for a few days and visited some ________.
| A．interest places | B．place of interests |
| C．places of interests | D．places of interest |
If you have headaches often, you need _______ .
| A．see a doctor | B．seeing a doctor |
| C．to see a doctor | D．not see a doctor |
He wasn’t _____ to understand the questions.
| A．quick enough | B．enough quick |
| C．quick as | D．quickly enough |
The strong young man can swim ______ the river.
| A．through | B．across | C．past | D．though |
The boss(老板) makes the workers _____ these machines(机器) for ten hours a day.
| A．make | B．to make | C．making | D．made |