— Who did it sound like? Anybody you know?

— Well, perhaps Jeff. I ____ who was calling before he hung it up. [ ]

A. must have asked

B. needn't have asked

C. couldn't have asked

D. should have asked

下图是呼吸系统的组成示意图。下列关于呼吸系统组成和功能的叙述，不正确的是

A．①是鼻腔，其黏膜分泌的黏液就是“痰液”

B．②既是食物的通道，也是空气的通道

C．⑥是呼吸系统的主要器官

D．人在吸气时，⑥扩张，气压减小