It was decades ago I was in my teens the Chinese government decided to reform the social economic system.
A. when; when
B. that; which
C. when; that
D. before; that
网友回答
A. when; when
B. that; which
(答案→)C. when; that
D. before; that
解析：when引导时间状语从句，二十年以前当我十几岁的时候。It was…that是强调句型。