北方地区多层砖混结构办公楼的楼地面净面积(不含楼梯面积)约占建筑面积的( )。

A．Graham never hesitates to help those in trouble.
B．Graham is always there for Fabian, no matter whether he is happy or sad.
C．Graham has just lost a game, but he tried to hide his sadness.

A．SecondaryNameNode
B．DataNode
C．TaskTracker
D．Jobtracker

A.辅助面积系数
B.建筑平面系数
C.平均单位建筑面积
D.建筑面积毛密度