A. That B. It C. As D. What
【答案】C 固定用法as is known to all：众所周知。本句的意思是：“众所周知，吸烟过多会引起肺癌。B 用于it is known to all that…句型。
2.The investigation, ___ will soon be published, was made by John.
A. at which the results B. the results on which
C. whose results D. at whose results
【答案】C 此句考查非限制性定语从句。C选项正确,whose在从句中作定语;whose results=the results of which =the results of the investigation,定语从句修饰investigation;B选项中的on改成of就对了。
3. ______ is well-known, the environment in China is badly in need of improvement.
A. It B. That C. As D. What
【答案】C此题考查的是as 引导的特殊定语从句。As is well known/ as is known to all/ as we all know：众所周知。
4. They overcame all the difficulties and fulfilled the plan ten days ahead of schedule, ____ was something we had not expected.
A. that B. this C. it D. which
【答案】D 逗号后为非限制性定语从句，只能由which 或者who 引导，不能用 that。
5. ____ is well known, light, like heat, is a form of energy.
A. It B. What C. Just as D. As
【答案】D句意为：“如我们所知，光跟热能一样是一种能量的形式。”as is well known 为非限定性定语从句，修饰整个主句，意为“如我们所知”;as 代表整个主句“光跟热能一样是一种能量的形式。”
6. The day breaks ________the birds are singing.
A. in that B. which C. on that D. in which
【答案】A 天亮了因为鸟儿在歌唱。in that 因为。
7. Liquids are like solids ______ they have a definite volume.
A. in that B. for that C. with that D. at that
【答案】A 液体像固体一样有确定的体积。in that 因为。
8. Criticism and self-criticism is necessary _____ it helps us to find and correct our mistakes.
A. by that B. on that C. on that D. in that
【答案】D 批评和自我批评很重要因为他帮助我们找出和纠正我们的错误。in that 因为。
9. Britain’s press is unusual ________ it is divided into two very different types of newspaper：the quality press and the popular press.
A. in how B. in what C. in which D. in that
【答案】D 英国出版社不同于普通出版社，它被分为两种不同种类的报纸，高质量的报纸和流行报纸。in that 因为。
10. The high income tax is harmful ______ it may discourage people from trying to earn more.
A. in that B. in which C. that D. which
【答案】A 高税收有害，因为他可能会挫伤人们试图挣更多钱的积极性。in that 因为。