Mike studied hard in the college, _____ contributed to his succe

Mike studied hard in the college, _____ contributed to his success in later life.
A、thus
B、therefore
C、which
D、it
【正确答案】：C
【题目解析】：非限制性定语从句，横向上的词代替前面的整个句子，在从句中作主语。