指代baby的代词常是it或者which，而非him或者she。
如：
The baby is crying，I wonder what's wrong with it.
英语中能做主语的代词有:
①人称代词主格：I ，he，she，we，they，you，it.
指示代词：this，that，those，these
不定代词：one，each，some，any，something，everything，nothing，anything
关系代词：which，that，who
②不定式
如：To do morning exercises is good for our health.
③动名词如：Seeing is believing.
④数词作主语，如：Two will be enough.两个就够了。
⑤名词化的形容词作主语
如：The blind and the lame are well cared for in our country.
⑥短语作主语，如：How to do well is an important question.
主语从句，如：That the earth goes/moves aroud the sun is
