18.A.Then
B.However
C.Therefore
D.Consequently
解：B
[解析]本题主要考查上下文的关系, 要注意however 是表示转折关系的词，therefore表示因果关系，而consequently也表示结果。
19.A.Since
B.Before
C.After
D.While
解：C
[解析]本文主要考查连词
20.A.initiated
B.invented
C.created
D.discovered
解：D
[解析]本文主要考查词义辨析，重点是：invent 和discover 的区别。Invent表示发明以前没有的东西，而discover 是指发现以前就存在的东西。
三、阅读理解
Passage 1
Albert Einstein had a great effect on science and history. An American university president once commented that Einstein had created a new outlook, a new view of the universe. It may be some time before the average mind understands fully the identity (特性) of time and space and so on — but even ordinary men understand now that the universe is something larger than ever thought before.
By 1914 the young Einstein had gained world fame. He accepted the offer to become a professor at the Prussian Academy of Science in Berlin. He had few duties, little teaching and unlimited opportunities for study, but soon his peace and quiet were broken by the First World War.
Einstein hated violence. The misery of war affected him deeply, and he sat unhappily in his office doing little. He lost interest in his research. Only when peace came in 1918 was he able to get back to work.
In the years following the First World War, honors were increasingly heaped on him. He became the head of the Kaiser Whilhem Institute of Theoretical Physics. In 1921 he won the Nobel Prize for Physics, and he was highly honored in Germany until the rise of Nazism (纳粹主义) when he was driven from Germany because he was a Jew.
21.The first paragraph is mainly about _____.
A.a new outlook of the universe
B.the feelings of an American college president
C.the change in human thought caused by Einstein
D.the difficulty in teaching Einstein's theory
解：C
[解析]本题是主旨题 第一段的主题句是第一句“Albert Einstein had a great effect on s
