单选题 — Can I speak to Mr. Liu. Please? — Sorry but he's busy ______ his guests now.
【正确答案】 C
【答案解析】[名师解析] 此题考查“be busy doing”的固定用法,表示“忙于……”。选项A为动词不定式,不符合语法,选项B“with”与busy搭配应为“be busy with sth.”而“his guest”是人不是物,所以不能选。故正确选项为C。