只具有信号放大和再生功能的集线器称为 【15】 。
参考答案：非智能集线器
Last Saturday, a snowfall shut down airport runways across Europe, _____ numerous flights. [ ]
A. causing
B. to cause
C. caused
D. having caused
足球比赛开球时，守方每一位队员需站在开球点（）
A.12m
B.10m
C.11m
D.9.15m
