The other day, Mum and I went to St. James's Hospital, and they did lots and lots of tests on me, ______are horrible and frightening.
【正确答案】
B
【答案解析】分析句子结构可知，逗号之后为非限制性定语从句。选项A、C、D均不能引导非限制性定语从句；which引导的非限制性定语从句用来说明前面整个句子的情况或主句的某一部分，本题中which指代前面的tests，most of which在从句中作主语。故选B。