More trees have to be planted to protect the environment and keep the b ______ of nature.

阅读下面一段文字，找出“碳链式反应”过程的三个关键性词语。

科学家在喀斯特地貌的研究中，发现了一个复杂的碳链式反应。当水流从空气中“大口吮吸”二氧化碳并侵蚀石灰岩时，持续不断的吸碳过程就开始了。接着，在岩石表面自由流淌的酸性水流携带着大量碳酸氢根，随着自然界的水循环转辗奔向江河湖海。此时，浮游植物体内的“食物加工厂”在急切地“找米下锅”，它们惊喜地发现，只要分泌一种叫做“碳酸酐酶”的催化剂，对水中的碳酸氢根“略施魔法”，等待加工的“米”——二氧化碳，就唾手可得。最终，光合作用将大量随波逐流的碳转化成有机碳，封存与水生植物体内。

Calileo lived in the city of Pisa, _____ there is a leaning tower about 180 feet _____.

A. in which; in which 　 B. where; in leight

C. which; high 　 　　　D. where; leight

Computer science__________(teach)now almost in all universities and institutes.

– Do you think it’s a good idea to make friends with your students?

-- _____, I do. I think it’s a great idea.

　 A. Really　　 B. Obviously　　 C. Actually　　　 D. Generally

______ people have come to realize the importance of learning English. Now they

go to various sorts of schools to take up English courses of one kind or another.

A. Hundred and thousand B. One hundred and thousand of

C. The large number of　 D. Hundreds of thousands of

The English Channel ________ the Great Britain ________ the Continent.

A. cuts; to 　　　　 B. divides; into 　 C. separates; from 　　 D. divides; from

The cause of his death __ his careless driving after too much wine.

A. led to　　　　　 B. caused　　　 C. lay in　　　　 D. resulted in

____ only book knowledge, you will not be able to work well.

A. Had　　 　B. Have　　 C. Having　 　　 D. To have

With so many problems to deal with, they____ another difficult year.

A. are having　 B. are to have　 C. are going to have　 D. have