——Do you know where David is? I couldn’t find him anywhere.

——Well, he_______ gone far—his coat’s still here.

A．shouldn’t have

B．mustn’t have

C．can’t have

D．wouldn’t have

下列哪些是喉痉挛的临床表现（）

A.呼气性呼吸困难

B.吸气性呼吸困难

C.吸气时高调哨鸣音

D.吸气时“三凹征”

E.发绀