题干
His sister had become a teacher , ______ was what he wanted to be.
A：who
B：whose
C：that
D：which
答案(点此获取答案解析）
D
A：who
B：whose
C：that
D：which
”和“ 
”分别表示两种不同元素的原子，其中表示混合物的是（ ）
