13. College students were a major force in the campaign, although participants of all ages were involved.

　　盡管參加這次運動的人涉及到各個年齡段的人，但是大學生是這場運動的主導力量。

　　14. thirty years later, the focus has changed but the urgency remains the same.

　　三十年之后，關注的焦點發(fā)生了變化，但其緊迫性依然。

　　15. X-rays were first discovered by a German scientist, Wilhelm Conrad roentgen, in 1895, almost by accident.

　　X射線最初是在1895年被一個德國科學家偶然地發(fā)現(xiàn)的，他的名字叫Wilhelm Conrad roentgen。

　　16. In fact, the rays could pass as easily through the fleshy part of his hand as through the black paper, but hardly at all through the bone.

　　事實上，就像穿過一張黑紙一樣，射線很容易穿過手部的肌肉，但卻根本不能穿過骨骼.

　　17. The answer would seem to lie in nuclear power stations.

　　看來問題在于核電站。

　　18. If the world population goes on increasing at its present rate, we may, in fifty years’ time, be burning up so much energy that we would damage the earth’s atmosphere.

　　如果世界人口繼續(xù)以當前這種速度增長的話，也許，五十年后，這樣燃燒如此多的能源將會致使我們破壞地球的大氣層。

　　19. Psychologists deal with the minds and behavior of people.

　　心理學家研究人們的心理與行為。

　　20. Several people have been instrumental in the field of psychology.

　　一些人在心理學領域起了很大作用。

　　21. It is only when we cannot see perfectly that we realize how important our eyes are.

　　只有當我們看東西不清楚時，我們才意識到我們的眼晴是多么地重要。

　　22. They can see things that are far away, but they have difficulty in reading a book unless they hold it at arm’s length.

　　這些遠視的人們能看清遠處的東西，但是他們讀書卻很困難，除非他們把書舉到一臂遠的距離處去看。

　　23. The same comment is made from generation to generation and it is always true.

　　同樣的理論代代相傳，而且總是正確。

　　24. Events that the older generation remembers vividly are nothing more than past history.

　　老一代記憶猶新的重大歷史事件對年輕人來說不過是過眼煙云而已。