3.
(teach) English is my job.
1
(teach) you English this term is my job.
doing作主语时，通常用以表示一件已知的ቤተ መጻሕፍቲ ባይዱ或经验。 to do通常用来表示一件未完成的事或目的。
doing 作主语时强调的是做那件事的持续状态， to do 作主语时主要表示现在或者将来的事情
• It seemed selfish of him not to share his dictionary with others.
=He seemed selfish not to share his dictionary with others.
1. 我花了一些时间才读完那段阅读材料。 2. 至少要九个钟头才能到那儿。 3. 跟着理智走，要有勇气，跟着感觉走，要
It + be + 形容词 + （for sb.）+ 动词不定式 这类句型常用形容词easy, difficult, hard, important,
possible，wise等作表语，为了强调不定式的逻辑主语， 常在不定式前加for sb，译为“对某人来说做某事怎么样”
It + be + 形容词 + of sb. + 动词不定式
1. 学一门外语非常重要。 2. 覆水难收。 3. 放弃这一机会是个遗憾。 4. 撒谎没好处。 5. 与其诅咒黑暗，不如燃起蜡烛。
It is very important to learn a foreign language. It is useless crying over the spilt milk. It seemed a pity to give up the chance. It is no good telling lies. It would be better to light up candle than to curse the darkness.
有倾其所有的决心。
It took me some time to read the reading materials. It takes at least nine hours to get there. It takes courage to follow your mind. But it takes everything to follow your heart.
It is + useless (senseless, nice, worth等形容词)+ doing sth．
It is hard to make him change him mind. It is no good objecting. It is useless speaking. It is not an easy thing to master a language. It is a great fun playing football． How would it be to start tomorrow? It is a waste of time trying to explain． It took all his strength to move out of the crowds. It is nice seeing you again． Business is business and it will not do to be so careless. It is no good pretending to know what you don't know. It is worth learning another language.
这类形容词常是表示心理品质,性格特征的形容词， 如：kind, nice stupid, clever, foolish, polite, impolite, silly, selfish, considerate等。某人和这些 形容词可以构成主系表结构。
如：
• It’s very kind of you to help me with the work. =You are kind to help me.
• It + takes + (sb.) + some time + to do sth. 表示“（某人）花多少时间干某事”的句 型，其中it是形式主语，代替后面的不定式 （to do sth.），句型中的sb.也可以省略。
It took me some time to read the reading materials. It takes at least nine hours to get there. It takes courage to follow your mind. But it takes everything to follow your heart.
todo和doing做主语的区别
1.
(climb) mountains is interesting．
1
(drive) a car during the rush hour must be
tiring．
2. _____computers is my job.
A.To sell B.Sell C.Selling D.Sold
It + be + 形容词/名词词组 + to do sth. / doing / that ….
不定式to do作主语时，常使用形式主语结构；而doing作 主语时，较少用形式主语结构，
只有在 It is + no use, no good (fun, a great pleasure, a waste of time...)等名词+doing sth.
逻辑主语
for the young, the children
It is useless crying over the spilt milk. It seemed a pity to give up the chance. It is no good telling lies. It’s very kind to help me with the work. It seemed selfish not to share his dictionary with others.