北京奥运会主体育场的外形像鸟巢，硼烷的结构也像鸟巢，故称为巢式硼烷，五硼烷（B5

内环境的下列变化中，能引起浮肿的是[ ]

A．尿素浓度降低

B．血糖浓度降低

C．钙离子浓度降低

D．血浆蛋白浓度降低

什么是返矿平衡？控制返矿平衡有何意义？

新生儿颌骨骨髓炎好发于（）。

A.上唇

B.下唇

C.上颌骨

D.下颌骨

E.颧骨

Hi, Celia!（）to the United States? It was wonderful. I really enjoyed it.

A.What was your idea 

B.How was your trip

C.Who went

D.How often did you travel

中心机房及场地的安全应考虑哪些因素？