No kidding?不是开玩笑吧?

A: I can finish two large pizzas in 10 minutes all by myself.

A: 我可以一个人十分钟内吃下二个大pizzas。

B: No kidding?

B: 不是讲笑呀?

这里的"No kidding?"也可说成"Are you serious?"、"Really?"、"Are you kidding me?" 之类的话。