两肺血减少,肺动脉段突出,两肺动脉干不对称,左侧粗,右侧细,见于哪种心脏病()
A.法洛四联征
B.动脉导管未闭
C.原发性肺动脉高压
D.肺动脉瓣狭窄
E.高位室间隔缺损
参考答案:D
A few people were killed in the fire, but _____ were saved.
A.the most
B.most of them
C.most of whom
D.most
真空系统内空气吸入量增加的原因是什么?