问题
选择题
Scientists have achievedr a major_______ in the search for a cure for cancer, _____ is good news for those who suffer from cancer
A．breakthrough; what
B．breakdown; which
C．breakup; that
D．breakthrough; which
答案
D
breakthrough 意思为 “突破”, a breakthrough in sth在某方面上的突破; which引导的非限制性定语从句, 指代前面句子的内容。