乙炔瓶卧放时,容易使()流出,造成燃烧和爆炸。
A、丙酮
B、甲烷
C、乙炔
D、以上选项都错误
参考答案:A
There was an _________ look on his face when he knew the bad grade of his son.
A.worrying
B.exciting
C.worried
D.excited
主动脉瓣关闭不全与主动脉瓣狭窄不同的是
A.心尖部第一心音减弱
B.早期五症状
C.有活动后呼吸困难
D.动脉枪击音
E.有心绞痛