“你凭什么这么说”英文怎么讲

How can you say that?
How could you say that?
By what did you say that?

都可以表达这样的意思.

(一楼给的可能出现在莎士比亚的剧本中,不属于现代英语用法)

What makes you say that?

How dare you say that?

How on earth are you saying that?

What makes you say so?
Whereby did you say so?
On what ground?

why do you say that?