中式英語口語糾錯:Be busy doing something

【中文這樣說】
    我哥哥一直在忙著準備他的期末考試.
    【英文對比翻譯】
    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為固定用法,中間不應(yīng)加in