有以下8种类型:
1) 名词,如:David arrived last night.
3)不定式,如: To do morning exercises is good for our health.
4)动名词,如: Seeing is believing.
6)名词化的形容词作主语,如:The blind and the lame are well cared for in our country.
7) 短语作主语,如 :How to do well is an important question.
8)主语从句 ,如:That the earth goes/movesaroud the sun is truth.