下列各项中，呼吸性酸中毒的常见病因是（）

A.发热

B.创伤

C.感染

D.精神过度紧张

E.气胸

.It was the practice _____ he got abroad _____ made him a good English speaker.

A．what; that

B．that; that

C．that; which

D．which; that