The police _____ the missing boy everywhere when he suddenly appeared in a theatre. [ ]

A. were searching for

B. are searching for

C. were searching

D. is searching for

闭合性气胸通常不表现下列症状（）

A.呼吸困难和发绀

B.突然发生

C.患区叩诊呈鼓音

D.患区呼吸音减弱

E.纵隔向患侧移位