直肠、肛管的动脉供应包括
A.直肠上动脉
B.直肠下动脉
C.肛管动脉
D.骶中动脉
E.以上都是
参考答案:E
解析:直肠、肛管的动脉供应血管主要包括以上四支。
It is the first time that a developing country _______ the Expo, described as the Olympic Games of economy, science and technology.
A.is hosting
B.has hosted
C.hosts
D.will host
化工用泵的检修需要抓好哪四个环节?