1.You_____________ (無論多么小心都不為過) when you drive a car.

cannot be too careful
解析:本題考查對cannot…too…結構的掌握。cannot…too…意為“無論…都不為過”，具有肯定的含義。相似的句子 還有：A woman cannot have too many hats while a man cannot have too many ties．(女人不嫌帽子多，男人不嫌領帶多。)

2.She never dreams of________________(夢見有機會) for her to be sent abroad very soon.

dreams of there being a chance
【解析】本題考查對短語dream of、there be句型和動名詞的掌握。“夢見，夢到”用dream of表示，后常接動名詞作賓語。 There is sth．for sb．表示“某人有某物”，故表示“她有機會”應該用there is a chance for her；而dream of后面要求接動名詞作賓語，故應將is改成being。另外，句尾的不定式是作a chance的定語，表示“被派往國外的機會”。

3.When he arrived, he found______________( 只有老年人和生病的人) at home.

none but the aged and the sick/only the aged and the sick
【解析】本題考查none but結構及形容詞名詞化用法的掌握。none but…意為“僅僅，只”。“定冠詞the+形容詞”可以表示一類人。類似的用法還有：the wealthy(富人)，the poor(窮人)，the handicapped(殘疾人)等。

4.All flights_________ (因暴風雪而取消), we decided to take the train.

having been canceled because of the snowstorm
解析:本題考查對獨立主格結構的掌握。前后分句主語不同且沒有連接詞，所以考慮用獨立主格做狀語表示原因。獨立結構的構成方式為：名詞/代詞(與句子的主語不同)+分詞/形容詞/副詞/不定式/介詞(短語)。flights與cancel之間是被動關系，且cancel這一動作發生在主句謂語decided的動作之前，所以謂語部分應用分詞的被動完成式.

5.The writer_____________ (如此專心致志地寫作) that he forgot to tap the ashes from his cigar.

was so absorbed in his writing
解析:本題考查對短語be absorbed in sth．/doing sth．的掌握，該短語意為“全神貫注于…，專心于…”。so強調程度深，與that構成so…that…句型，表示“如此…以至于…”.