study的過去式？

　　雙語例句

　　1.She gave up her studies to have Alexander.

　　為了生亞歷山大，她放棄了學業。

　　2.She is currently doing a business studies course at Leeds.

　　她目前在利茲大學修讀一門商科課程。

　　3.Debbie studied her friend's face for a moment.

　　黛比仔細端詳了一會她朋友的臉。

　　4.I know that you've been studying chimpanzees for thirty years now.

　　我知道你研究黑猩猩至今已有30年了。

　　5.I invite every citizen to carefully study the document.

　　我請每位市民都仔細研讀該文件。