I didn't know I wasn't supposed to. (我不知道不能这样做。)

　　What made you do that?

　　Why did you do something like that?

　　How could you?

　　How could you do that?

　　是什么原因呢?

　　What causes it? *cause“成为……的原因”、“引起”。

　　The river is getting dirty. (那条河越来越脏。)

　　What causes it? (为什么会这样呢?)

　　What causes it? (是什么原因?)

　　Air pollution. (由于空气污染。)

　　What is it caused by?

　　请给我解释一下。

　　Explain it to me.

　　You'd better start explaining.

　　为什么不行?

　　Why not? *在被对方否定时，反驳对方“为什么不行?”，还含有“当然可以”、“同意”的意思。

　　You can't wear the red pants. (你不能穿那条红裤子。)

　　Why not? They're my favorite. (为什么不能?这是我最喜欢的裤子。)

　　Why can't I?

　　Is there a reason? (有理由吗?)

　　你怎么那么高兴?

　　What are you so happy about?

　　What are you so happy about? (你怎么那么高兴?)

　　It's a wonderful day. (今天是最棒的一天。)

　　You seem especially happy today. (你今天显得特别高兴。)

　　What makes you so happy? *更随意的说法。

　　为了什么?

　　What for?

　　I made this big box! (我做了个这么大的箱子。)

　　What for? (干什么用?)For what?

　　What is this for? (这个用来干嘛?)

　　为了谁?

　　For who?

　　I bought this gift today. (今天我买了一份礼物。)

　　For who? (给谁买的?)

　　Who is it for?