Where is the canteen? It's ___ the first floor. [ ]
A. at
B. in
C. on
答案：C
患者，女，29岁，G2P037周孕，胎儿宫内。拟在腰硬联合阻滞麻醉下行剖宫产术。麻醉成功后，HR上升至120次/min，，Bp降至70/45mmHg，其出现的原因之一是因为增大的子宫压迫了（）
A.下腔静脉
B.髂内静脉
C.髂外静脉
D.髂总静脉
E.子宫静脉
For a floating vessel, the center of buoyancy and the metacenter are in the line of action of the buoyant force（）.
A.only when there is positive stability
B.only when there is negative stability
C.only when there is neutral stability
D.at all times
