对于大型的建筑,传输距离长,为了尽可能的减少传输损耗,采用光纤传输信号,光纤的传输损耗是2dB/1000m,此外光纤重量轻,体积小便于施工。()
参考答案:对
Children should be encouraged to help their parents,which________helps them to learn how to
cooperate and share. [ ]
A. in return
B. in addition
C. in brief
D. in turn
毒性反应()
A.与药物剂量无关
B.与药物的使用时间无关
C.常造成机体的生理性损害
D.大多为难以预知的反应
E.有时也与机体高敏性有关