根据下列文章,请回答 51~65 题。
The Development of Rubber
Here is the story of rubber. From the earliest time it was common knowledge _________ (1) the Peruvians that when a cut was made in the outside skin of a rubber tree, a white liquid _________(2) milk came out, and that _________ (3) 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 _________ (4). The Peruvians made the_________ (5) 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 _________ (6) 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 _________(7), and our raincoats are still named after him.
But these first rubber overshoes and raincoats were all soft and sticky in summer, and _________ (8) 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), _________ (9) very strong -- even in the warmest summer and the coldest winter. This was made_________ (10) by a man called Goodyear. After many_________ . (11), 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_________(12).
A friend of his, Nicholas Hayward, had the idea in his sleep that rubber' might be made hard and strong if mixed with sulphur (硫磺) and put in the sun. Goodyear put this idea_________ (13) 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 _________ (14) to make rubber hard and strong is by heating it with sulphur. It took Goodyear four more years to find this method. When at last he did it, he had _________ (15) at all. Everything of the smallest value had been used to get money, even his sons' school-books.
第 51 题
A.for
B.to
C.about
D.with
第1题
B.在特大城市和大城市本地网中,为了减少一次呼叫中的串接段数,可以采用来话汇接、去话汇接、集中汇接、双汇接局等汇接方式
C.在长途网中,为了减少一次呼叫中的串接段数,根据话务关系的密切程度和经济上的可行性,可以建立省间的DC1与DC2之间的低呼损直达路由和省间的DC2之间的高效或低呼损直达路由
D.在长途网中,为了减少一次呼叫中的串接段数,在DC1间建立树状网连接
第2题
A.在长途网中,为了减少一次中的串接段数,在DC1间建立网状网连接
B.、在特大城市和大城市本地网中,为了减少一次呼叫中的串接段数,可以采用来话汇接、集中汇接、双汇接局等汇接方式
C.在长途网中,建立省间的DC1与DC2之间的低呼损直达路由
D.在长途网中,建立省间的DC2之间的高效或低呼损直达路由
第4题
用球隙测量交直流电压时,关于串接保护电阻的说法,下面哪些是对的?()
A 球隙必须串有很大阻值的保护电阻
B 串接电阻越大越好
C 一般规定串联的电阻不超过500Ω
D 冲击放电时间很短,不需要保护球面。
第5题
A.球隙必须串有很大阻值的保护电阻
B.串接电阻越大越好
C.一般规定串联的电阻不超过500
D.冲击放电时间很短,不需要保护球面
第8题
下面关于串级控制回路的描述中正确的是()
A、主、副控制器串接工作的双闭环负反馈控制系统
B、主、副控制器串接工作,主控制器的输出直接操纵控制阀
C、主、副控制器串接工作,实现对副变量的定值控制
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