study的过去式英语是什么

　　She studied chemistry for three years.

　　她学了三年化学。

　　I studied English and Drama at college.

　　我在大学学的是英语和戏剧。

　　My brother studied at the Royal College of Art.

　　我哥哥曾就学于皇家美术学院。

　　The report found that 30% of the firms studied had failed within a year.

　　据报告称，受调查的公司有30%一年内倒闭了。

　　He studied politics and economics at Yale.

　　他曾在耶鲁大学学习政治学和经济学。