3 because：因为，连接原因状语从句

She didn't go there，because she was ill.

因为她病了，所以她没去那儿。

1.回答Why问句时，只能用because，不能用for或 as.

Why are you late?

你为什么迟到?

Because I met a traffic accident on my way here.

因为在我来这儿的路上，遇到了车祸。

2.汉语中，我们经常说因为……所以，但在英文中有了because，就不能再用so。

(×)Because he was tired， so he couldn't walk there.

因为他累了，所以他不能走到那儿了。

4 if，though (although)

If it doesn't rain，we'll go to the park.

如果不下雨，我们就去公园。

Though I was tired， I still worked hard.

虽然我很累，可是我仍然努力地工作。

1.if：如果(引导条件从句)

You can pass the exam if you study hard.

如果你努力学习，你会及格的。

2.though，although：虽然(引导让步状语从句)和原因状语从句一样，如果用了though，although (虽然)就不能再用but(但是)。

Although(Though) I live near the sea， I'm not a good swimmer.

=I live near the sea，but I'm not a good swimmer.

虽然我住在海边，可是我游泳并不好。

注意

注意时态一致，和时间状语从句一样。主句是将来时之时，从句要用一般现在时。

5 so…that：太……以致……

He is so old that he can't work. = He is too old to work.

他太老了，不能工作。

The box is so heavy that I can't lift it.

=The box is too heavy for me to lift.

箱子太沉了，我抬不起来。

The girl is so beautiful that everybody likes her.

这个小女孩太漂亮了，每个人都喜欢她。

注意

注意此句型与too…to的互换。

so…that在肯定句中不能转换成too…to…。

三 连词比较

I　and 与or

1) 并列结构中，or通常用于否定句，and用于肯定句。

2) 但有时and 也可用于否定句。请注意其不同特点：

There is no air or water in the moon.

There is no air and no water on the moon.

在否定中并列结构用or 连接，但含有两个否定词的句子实际被看作是肯定结构，因此要用and。

典型例题

---I don't like chicken ___ fish.

---I don't like chicken, ___ I like fish very much.

A. and; and　 B. and; but　C. or; but　D. or;and

答案C。否定句中表并列用or, but 表转折。

判断改错：

(错) We will die without air and water.

(错) We can't live without air or water.

(对) We will die without air or water.

(对) We can't live without air and water.

3 )表示选择的并列结构

(1) or　意思为"否则"。

I must work hard, or I'll fail in the exam.

(2) either…or　意思为"或者……或者……"。注意谓语动词采用就近原则。

Either you or I am right.