作者：余扬
别看it貌不惊人，但它的作用可不小。不信，就让我们一起来关注"它"的用法！
一、 用于指除人以外的一切生物、无生命的东西和事情。如：
Look at the rain!It's heavy, isn't it?
二、 用于指代人。常指代说话者心目中不太清楚的人或性别不详的婴幼儿。如：
a. -Who is it? -It's me.
b. -Who is the baby in her arms? -It's Jim.
三、 用于指时间、距离和自然现象等。如：
-What time is it? -It's ten.
It is very quiet here at the moment.
四、 用作形式主语。it作形式主语时无意义，真正的主语由后面的动词不定式短语、动名词短语或从句来充当。如：
It's important for us to keep the water clean.
It seems that he is ill. = He seems to be ill.
五、 用作形式宾语。it作形式宾语时，常用在think, find, make, feel等词的后面。常用的固定句型为：主语+谓语+it+宾语补足语+动词不定式/动名词/从句。如：
We think it no good reading in bed.
六、 用在强调结构中。在强调结构中，用it引导出被强调的部分，结构为：It+be+被强调的成分+who/that...。如：
It was they who/that helped me in the street this evening. 是他们今天晚上在街上帮助我的。
It was me that they helped in the street this evening. 今天晚上他们在街上帮助的人是我。