综合布线系统以什么为传输介质,采用分层星型结构?()
A、非屏蔽双绞线和光纤
B、屏蔽双绞线和光缆
C、非屏蔽双绞线和光缆
D、屏蔽双绞线和光纤
参考答案:C
My father _______ in the morning, but now he ____________ after supper.
A.is used to run; is used to walking
B.used to run; is used to run
C.used to run; is used to walking
D.is used to running; used to walk
设∑为柱面x2+y2=1介于z=0与z=2-x之间部分,有均匀面密度ρ(常数),则∑的质量M=______.