improve的名詞形式是什么

　　An improvement in living standards could be years away.

　　生活水平的提高可能還要幾年。

　　We expect to see further improvement over the coming year.

　　我們期望來年會有更進一步的改善。

　　CBS's ratings again showed huge improvement over the previous year.

　　哥倫比亞廣播公司的收視率比過去的一年又有了大幅提高。