it有三种常见用法，第一种是它最普通的用法作为代词，代指的是动物的它，物体的它，第二种用法it用在形式主语当中，记住形式主义就不能叫代词了，它是一个形式主语，第三种用法it还可以表示一个很虚的主语。
扩展资料
例句：
It doesnt have the market to itself.
它未能独占市场。
She lost it, just as I said she would.
我就说了吧，她把它丢了。
It was a time of peak demand for the product.
那是对该产品需求最旺的时期。
It is less of a problem than Id expected.
问题不像我预料的那么大。
It is estimated the project will last four years.
据估计，这项工程将持续四年。
