essential

英语里有些形容词在意义上与情态或意愿有关,如 essential(重要的,不可少的),important(重要的),necessary(必须的),imperative((非常必要的),vital(至关重要的),impossible(不可能的),obligatory(必须的),appropriate(适当的),advisable(明智的),desirable(好的,所希望的),preferable(更好的)等等。当用先行词 it 充当主语而用它们充当表语时,则 that 从句的谓语动词或者用现在时虚拟式(在美国英语里),或者用 should + 动词原形(在英国英语里):

1. It was essential that he find the tomb first. (Dan Brown, The Da Vinci Code) 他就得先找到这座骑士坟墓。(《达·芬奇密码》)

2. It's imperative that you should not be seen here. (LDCE) 你必须马上离开这里。

3. It is vital that Mr Jones should receive this letter before this evening. (JED) 重要的是琼斯先生在今晚以前要收到这封信。

4. It is necessary, absolutely, that I should return it this morning. (Bennet) 我绝对必须在今早把它还回去。

5. It's advisable that everyone should have a map. (PEG) 最好每个人手里都有一张地图。

6. It is most desirable that he should attend the conference. (ALD) 最大的希望是他能来参加会议。

7. It is appropriate that this tax be abolished. (CGEL) 废止这条税收是适宜的。

8. It is imperative that they arrive on time for the lecture. (TOEFL) 他们必须准时来听课。请做下面的试题：

9. It is ____ that the meeting be closed. A. important B. good C. useful D. nice(TOEFL 教程)

10. It is ____ that the meeting be closed. A. nice B. useful C. right D. imperative(TOEFL 教程)

11. It is necessary $\$frac{that}{A} she comes here twice a week to help do the room. (EPT)