He made a mistake but then he took action to change the situation it got worse. A. until

问题补充：

He made a mistake, but then he took action to change the situation it got worse.

A. until

B. when

C. before

D. because

答案：

A. until

B. when

(答案→)C. before

D. because

解析：句意：他犯了一个错误，但他在它变得更糟前采取了行动改变现状。Until直到；when当···时；before在···之前；because因为。根据句意可知选C。