机械呼吸阀应安装在拱顶油罐的顶部()位置。
A.中央
B.边缘
C.侧面
D.中央与边缘之间
参考答案:A
"_____ you've made! But you should work still harder," Dad said to me.[ ]
A. What big mistake
B. How big mistakes
C. What great progress
D. How great progress
血流速度最慢的是()
A.主动脉
B.微动脉
C.毛细血管
D.微静脉
E.腔静脉