题目

由交变电流的电压瞬时值表达式u=14.14sin4πt可知（）A.此交变电流的频率是4HzB.此交变电流的周期是0.5sC.当t=0时，此交变电流的电压有最大值D.当t=0.5s时，产生此交变电流的线圈平面与中性面垂直 答案：B【试题分析】When________, the museum will be open to the pulic next year.A. to be completed. B. completingC. being completed D. completed