28．You ______ very fast if you went from New York to Boston in six hours．
| A．should drive | B．would have driven |
| C．may drive | D．must have driven |
He waited with his companion_________the rescuers came, and then helped them carry her back down the mountain.
| A．when | B．until | C．unless | D．while |
It's_________for an employee of this company to work seventy" hours a week since the competition is fierce in the industry.
| A．ordinary | B．usual | C．average | D．regular |
_____the 19th-century America, the novel Gone with the Wind tells the story of a woman facing war and starvation bravely.
| A．Set up | B．Set down | C．Set in | D．Set off |
You did me a huge favor. However, I lack words_________to express my thanks.
| A．through which | B．with which | C．where | D．for which |
Tom was running out of time in the exam, but there still remained several questions_________.
A. to be answered B. to answerC. answered D answering