高度是从（）量至一个平面、一个点或作为一个点的物体的垂直距离。
A.平均海平面
B.标准海平面
C.机场标高点
D.跑道入口平面
参考答案：A
E-mail, as well as telephones, _____ an important part in daily communication. [ ]
A. is being played
B. are playing
C. have played
D. is playing
妊娠腹痛的辨证要点及治疗原则是什么？
