管件中连接管路支管的部件称为()。
A、弯头
B、三通或四通
C、丝堵
D、活接头
参考答案:B
Considering the general circulation of the atmosphere,the wind system between latitudes 30°N and 60°N is commonly called the().
A.prevailing westerlies
B.horse latitudes
C.trade winds
D.subpolar low pressure belts
物联网的特征在于()的叠加。
A.感知
B.互联
C.智能
D.网络