冠詞a后面加什么詞性

　　I didn't get a red cent for all my work.

　　我做了那么多工作，可什么也沒得到。

　　You need three A levels to get onto this university course.

　　你要參加這個大學教程，就需要通過三科高級證書考試。

　　A number of measures were taken to alleviate the problem.

　　采取了一系列措施緩解這個問題。

　　She's a changed woman since she got that job.

　　她自從得到了那份工作，變得判若兩人。

　　A free trade agreement would be advantageous to both countries.

　　自由貿易協定對兩國都會有利。