6. Suppose there were a flood or an earthquake and the people could not be reached by trains or trucks. _______ packages of food could be dropped from planes, the people might starve.

A. Until B. Before C. Unless D. If only

7. Mary has long had the desire _______ a famous writer even though the study of writing would require years of sacrifice on her part.

A. for becomingB. to become

C. of becomingD. becoming

8. This is so difficult a problem that the scientist is known to _______ on it for about ten years, but hasn’t found a solution yet.

A.have worked B. have been working

C.be working D. work on

9. A majority _______ collectively may be regarded as a being whose opinions and, most frequently, whose interests are opposed to those of another being, which is styled a minority.

A. taking B. takes C. take D. taken

10. I would have passed the college entrance examinations _______ I missed some of the questions and gave the wrong answers.

A. butB. because C. as D. in that

6. Cunless“除非”，从主从句的逻辑关系上看是惟一正确选择。句意：“假如发生了水灾或地震，且火车、汽车又无法通至灾区，除非用飞机空投，否则那里的人们就会饿死。”

7. Bto become在句中做desire的定语，意为“成为一个著名作家的愿望”，其他结构一般不做desire的定语。

8. B不定式to have been working…做主语scientist的补足语，用完成进行式表示：“这个科学家已对如此复杂的问题研究了大约十年，并且还要继续研究下去。”

9. Dtaken在句中做后置定语，修饰majority, 由于与所修饰的词是动宾关系，所以应用过去分词，a majority which is taken collectively可以理解为“(把)大多数人作为一个整体”。

10. A句中but表示转折，后面陈述的是事实情况：“……看错了问题所以没答对”。暗指“若不是看错了题，就会答对而且通过考试”。因此句子前半部分用的是虚拟语气would have passed。