I'm sorry to have taken your umbrella ________ because I mistook it ________ mine.

A.for mistake; as

B.with mistake; with

C.by mistake; for

D.out of mistake; about

答案及解析： C

解析：

由句意来判断。by mistake意为“错误地”；

而mistake sth. for…意为“把……误以为……”。