完形填空(第51一65题，每题l分，共15分)
下面的短文有15处空白，请根据短文内容为每处空白确定1个最佳选项。
The Development of Rubber
Here is the story of rubber. From the earliest time it was common knowledge_________ (51)the Peruvians that when a cut was made in the outside skin of a rubber tree, a white liquid_________(52) milk came out, and that_________(53) this a sticky (粘的) mass of rubber might be made. This rubber is soft when warm, so that it is possible to give it any _________ (54). The Peruvians made the _________ (55) that it was very good for keeping out the wet. Then in the early 1800's, the Americans made use of it for the first time.First they made overshoes to (56) their feet dry.Then came a certain Mr. Mackintosh, who made coats of cloth covered with natural rubber. From that day to this we have been coating cloth with rubber as Mr. Mackintosh _________ (57), and our raincoats are still named after him.
But these first rubber overshoes and raincoats were all soft and sticky in summer, and _________ (58) and inelastic (无弹性的) in the winter when it was cold. But the rubber we have today is soft and elastic(有弹性的), _________ (59) very strong m even in the warmest summer and the coldest winter. This was made _________ (60) by a man called Goodyear. After many_________ (61), he found that nitric acid (硝酸) made the rubber much better, but it is not hard and strong enough.Then a strange thing took _________ (62). A friend of his, Nicholas Hayward, had the idea in his sleep that rubber might be made hard and strong if mixed with sulfur (硫磺) and put in the sun. Goodyear put this idea _________ (63) the test, and saw that it did have more or less the desired effect though somewhat less than more. The only effect it had was on the outside of the rubber. It is common knowledge now that the (64) to make rubber hard and strong is by heating it with sulfur. It took Goodyear four more years to find this method. When at last he did it, he had _________ (65) at all. Everything of the smallest value had been used to get money, even his sons' school-books.
51. A. for
B. to
C. about
D. with
52. A. like
B. alike
C. resembled
D. similar
53. A. on
B. from
C. up
D. in
54. A. use
B. heat
C. pressure
D. form
55. A. creation
B. invention
C. discovery
D. recognition
56. A. retain
B. keep
C. hold
D. set
57. A. did
B. built
C. tried
D. conducted
58. A. weak
B. gentle
C. hard
D. strong
59. A. or
B. however
C. though
D. even
60. A. capable
B. probable
C. practical
D. possible
61. A. experiments
B. checks
C. discoveries
D. works
62. A. form
B. place
C. shape
D. size
63. A. on
B. to
C. in
D. with
64. A. system
B. style
C. way
D. direction
65. A. everything
B. anything
C. nothing
D. something