单选，急求答案及原因，详细一点，谢谢

Answer 1

1. It was not until she arrived in class __________ she realized she had forgotten her book.
A) and B) then C) when D) that
D, It is/was...that.... 强调结构
2. __________ deserves the award will certainly get it.
A) Who we think B) Whoever we think
C) Whoever we think of D) whoever do we think
D， do we think 插入语，可以不理，whoever =anybody who 引导一个主语从句。
3. Their qualification __________ them to a high salary.
A) rewards B) grants
C) entitles D) awards
C, entile，使有资格。
4. Ted has told me that he always escapes __________ as he has a very fast sports car.
A) to fine B) to be fined
C) being fined D) having been fined
D, 我不是很确定
5. The student in the dormitories were forbidden, unless they had special passes, __________ after 11 p.m.
A) staying out B) by staying out C) to stay outD) from staying out
D, forbide sb, from doing sth 禁止某人做某事
6. Living in such a high place as Tibet has its problems, __________ obtaining oxygen is not the least.
A) of which B) for what C) as D) whose
A, 这里是个分限制性定语从句，of which=where意为"在这些问题里面”表示所属关系我们用介词of。
7. The railway ticket for one single journey between Beijing and Shanghai is __________ for five days.
A) fruitful B) beneficialC) valid D) effective
C, 有效的，有用的，
8. Scientists generally agree that the Earth’s climate will warm up over the next 50 to 100 years __________ it has warmed in the 2000 years since the Ice Age.
A) as long as B) as much as C) as soon as D) as well as
D， as well as 像......一样
9. You’d better come tomorrow, __________?
A) didn’t you B) couldn’t you C) wouldn’t you D) hadn’t you
D， 这里had最为一个助动词。
10. He has been in China for a year and studied the market to discover the __________ for profitable investment.
A) necessity B) reality C) capacity D) potential
D， 投资的可能性。

11. Venice is one of the most beautiful cities __________ .
A) over Europe B) in Europe C) all over Europe D) on Europe
12. Since it is already midnight, we __________ .
A) had better left B) ought to have left C) should have taken our leave D) might as well leave