what are you doing do为什么加ing

what are you doing do为什么加ing What are you doing为什么要加ing how are you doing?为什么do要加ing?而How do you do的do就不需要? What were you doing at 7:30 last night? 请问do为什么加ing 英语中的问题英语中What do you like doing?中的doing为什么要加ing呢? what are you doing for vacation?doing为什么用ing形式啊 What are you talking about?为什么talk加ing 英语为什么要What are you doing?而不是What do you doing?我经常把are和do 弄混 what do you t-----you are doing what do you think you are doing what are you doing for vacation为什么用ing形式和for啊 Don't let me catch you doing that again.do为什么加ing呢?能不能不加呢.