中式英语口语纠错:Be busy doing something

【中文这样说】

我哥哥一直在忙着准备他的期末考试.

【英文对比翻译】

Chinese Style My brother has been busy in preparing for his final examination.
American Style My brother has been busy preparing for his final examination.

Be busy doing sth为固定用法,中间不应加in