The old couple have been married for 40 years and never once ________ with each other.

A．they had quarrelled

B．they have quarrelled

C．have they quarrelled

D．had they quarreled

患者，女性，51岁，肺结核伴咯血，最危险的并发症是（）

A.窒息

B.出血性休克

C.失血性贫血

D.继发感染

E.结核播散