Unit 3 A healthy life Section Ⅲ Grammar——it 的用法(Ⅰ)一、it 用作代词1．it 用作人称代词：(1)指代前面的名词或前面提到过的事；(2)指代性别不明的 child 或 baby；(3)指代未出场的身份不明确的人。如：My friend offered me a beautiful gift yesterday, and I like it very much.我朋友昨天给了我一件漂亮的礼物，我非常喜欢。His sister has given birth to a baby recently. It is said it is very beautiful.他姐姐最近生了个孩子。据说孩子很漂亮。—Who is waiting for you at the bus stop?—I have no idea. It may be my brother.“谁正在公共汽车站等你？”“我不知道。可能是我哥哥。”2．it 用作非人称代词：(1)it 可以表示天气、时间、距离、自然现象、环境情况等；(2)it 也可以表示一般的、笼统的情况。如：It is a fine day today, isn't it?今天是个好天气，对吧？It is five kilometres to the town from the village.从村庄到城镇有 5 千米的路。It's ten o'clock now.现在 10 点钟了。It is too bad. There is much work for me to do today.糟透了。今天我有太多的工作要做。3．it 可以指代指示代词 this, that 或不定代词 something, nothing。如：Whenever she sees something that she likes, she goes and buys it.每当她看到了喜欢的东西，她就会去买下来。二、it 用作引导词1．it 在句中作形式主语：it 作为形式主语常用于下面句型中：(1)It be＋adj.＋(for sb.) to do...(对某人来说)做……是……的。(常用于此句型的形容词有 possible, necessary, important, easy, strange, natural 等)(2)It be＋n.＋doing...做……是……的。(常用于本句型的名词有 good, use 等)(3)It be＋adj.＋doing...做……是……的。(常用于本句型的形容词有 useless, worthwhile 等)(4)It be＋adj.＋that...(对某人来说)做……是……的。(常用于此句型的形容词有necessary, important, strange, natural 等)注意：此句型中从句一般用虚拟语气，即(should) do。(5)It be＋过去分词＋that...据……。(常用于本句型的过去分词有 said, announced, believed, reported, known, hoped 等)(6)It be＋n.＋that...做……是……的。(常用于此句型的名词有 pity, honour, shame,...
