1. 名词作主语
2. 代词作主语
3. 动名词或不定式作主语
4. 名词性从句作主语
5. 名词短语作主语
其中名词短语是由“疑问词+不定式组成”
如:
- 1 疑问副词
where to live - 2 疑问代词
what to do
6. 表距离的地方副词作主语
如 : From Beijing to Shanghai is about 1000 kilometers.
或者写成: It is about 1000 kilometers from Beijing to Shanghai.