心包积液最常见的原因是（）
A.风湿性
B.结核性
C.化脓性
D.类风湿性
E.心包转移瘤
参考答案：B
The solider had qualified as a doctor, but later he gave up the _______of medicine for full-time training.[ ]
A. fight
B. treatment
C. practice
D. design
煤气管道为什么要安装氮气接头？
