it用法？

　　例句：

　　It doesn't 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 I'd 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。