u一、考点聚焦
1、it的基本用法
（1）用作人称代词，代替前文提到过的事物。
The train has arrived. It arrived half an hour ago.
（2）用以代替提示代词this, that。
—What’s this? —It’s a knife.
—Whose watch is that? —It’s mine.
（3）起指示代词的作用，指一个人或事物。
—Who is knocking at the door? —It’s me.
（4）指环境情况等。
It was very noisy (quiet) at the very moment.
（5）指时间、季节等。
—What time is it? —It’s eight o’clock.
It often rains in summer here.
