答案：C

考察句子结构。the suffering 为先行词，后面“______ has caused ”是由that引导的宾语从句，在从句中作宾语，代替the suffering 。that在定语从句中作宾语时可省略，该宾语从句的主语是     The financial crisis ，由it代替。本句补充完整为       The financial crisis and the suffering that it has caused have a great influence on the whole world.故答案为C。