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：
试题分析: 句意：他犯了一个错误，但是之后在形式变坏之前他采取了行动去改变。until直到，when当……的时候， before在……之前，because因为；make a mistake犯错，take action采取行动；根据语境可知是在情况变的更糟糕之前采取行动，故选C
