题干
— Dad, when will you be free? You agreed to go to the seaside with me two days ago.
— I’m sorry, Jean. But I think I’ll have a ________ holiday soon.
A：four- days
B：four-day
C：four days
D：four day
答案(点此获取答案解析）
B
分别代表不同种类元素的原子，其中可能属于氧化物的是（ ）