题干
— I ‘ll ask our physics teacher to explain Newton’s Second Law of Motion, which she taught us yesterday.
— That’s just _______ most of the students haven’t understood.
— That’s just _______ most of the students haven’t understood.
A：what
B：why
C：how
D：where
答案(点此获取答案解析）
A
②苯 ③甲苯 ④CH2=CH—CH=CH2 ⑤乙烯