Unit 4 Astronomy: the science of the stars(Period 3　Learning about language: Grammar)

由whether引導的主語從句放在句首、句末都可。
whether it will please them is not easy to say. /it is not easy to say whether it will please them.
很難說這會不會使他們高興。
2) 連接代詞 who, what, which, whoever, whatever, whichever等。
what seems easy to some people seems difficult to others.
對某些人看來很容易的事, 對另外一些人可能很困難。
3) 連接副詞 when, where, how, why等。
why he did it remains a mystery.
他為什么做那件事依然是個謎。
（2）位置
主語從句可以前置, 也可以后置。用it作形式主語, 而把主語從句放在句末, 常用下面幾種句型:
1) it+be+表語+主語從句
it is still uncertain whether he is coming or not.
他是不是來還沒有確定。
2) it+不及物動詞+主語從句
it happens that they were absent.
他們碰巧缺席了。
3) it+及物動詞（被動語態(tài)）+主語從句
it has been decided that the exhibition will not open on sundays.
現(xiàn)經(jīng)決定展覽會星期日不開放。
注意:
1) 主語從句在句首時, 必須由連接詞引導, 不能省略這些連接詞; 但是如果用it作形式主語, 而把主語從句放在句末時, 從屬連詞that可以省略。
他們相互喜愛是很自然的。
誤: they should like each other is natural.
正: that they should like each other is natural.
正: it is natural (that) they should like each other.
2) 如果主語從句放在句首, 不能用if引導; 但是如果用it 作形式主語, 而把主語從句放在句末時, 也可以用if引導。
瑪麗是不是真聽見他了, 很值得懷疑。
誤: if mary really heard him is really doubtful.
正: whether mary really heard him is really doubtful.
正: it was doubtful whether/if mary really heard him.
→step 4 grammar practice
1. turn to page 29. ask students to do exercise 2 and exercise 3 in discovering useful structures. first let them finish them individually. then check the answers with the whole class. give some explanations if necessary.
2. turn to page 64. ask students to do exercise 1 and exercise 2. check the answers after most of them finish.
→step 5 discussion
let students have a discussion in groups. the topic is “my problem”. one talks about the problems in his study or life. the others should give some advice or suggestions. remind students to use the following structures:
(show the following on the screen to help students. )
the fact is/it is a fact that. . .
the difficulty is. . . /what i find difficult is. . .
the trouble is. . . /what worries me is. . .
my suggestion is. . . /what i would suggest is. . .
my advice is. . . /what i would advise is. . .
i think that. . . /what i think is. . .
i want to tell you that. . . /what i want to say is. . .
→step 6 closing down by a quiz
show the following exercises on the screen. let students finish them within three minutes. three minutes later, check the answers with the whole class.