主語從句中的虛擬語氣
1)It is(was)+suggested+that+(should)+動(dòng)詞原形。如：
It is proposed that more selective courses be offered next year.
It has been decided that a special committee be formed tosupervise the work.
2)It is(was)+形容詞+that+(should)+動(dòng)詞原形。
該句式中的形容詞一般包括：advisable, appropriate, desirable, essential, important, imperative,necessary, impossible等。例如：
It is important that the students take brief notes while listening to the lecture.
It is essential that all the facts be examined first.
近義詞辨析
obvious, apparent, evident, clear這組詞均含有“明顯的”的意思。
obvious指被覺察的東西具有顯著特點(diǎn)，不需費(fèi)力就可覺察到，常用于一目了然的事物。
apparent意為表面看起來很明顯，而實(shí)際情況未必如此。
evident指有證據(jù)作出合理判斷，考慮到各種事實(shí)、條件后而顯得明顯。
clear指不存在使人迷惑或使問題復(fù)雜化的因素。
It was an obvious mistake for him to have gone alone.他獨(dú)自一人去，這是一個(gè)明顯的錯(cuò)誤。
It was becoming increasingly apparent that he disliked me.他不喜歡我這一點(diǎn)變得越來越明顯。
The applause made it evident that the play was a hit.掌聲明顯地表明這部劇引起了轟動(dòng)。
The situation is clear to everyone.局勢(shì)大家都清楚。