题干
They have made greater progress than________ .
A：they had expected
B：expected
C：to be expected
D：expecting
答案(点此获取答案解析）
B
A：they had expected
B：expected
C：to be expected
D：expecting
和一个－Cl，它的可能的结构有几种(本题不考虑对映异构体)（ ）