16. 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
17. 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 becoming
B. to become
C. of becoming
D. becoming
18. 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
19. 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
20. I would have passed the college entrance examinations _______ I missed some of the questions and gave the wrong answers.
A. but
B. because
C. as
D. in that
