it用法？

例句：

It doesn't have the market to itself.

它未能獨佔市場。

She lost it, just as I said she would.

我就説了吧，她把它丟了。

It was a time of peak demand for the product.

那是對該產品需求最旺的時期。

It is less of a problem than I'd expected.

問題不像我預料的那麼大。

It is estimated the project will last four years.

據估計，這項工程將持續四年。