He studied at a famous college when he was young, ______ contributed to his success in later life.

【正确答案】 A

【答案解析】 语法知识。此句为主从复合句，空格所属的从句为定语从句。连接两句的标点符号为逗号，可知从句为非限制性定语从句，只能由which引导。故答案为A。