Nobody knew who was the first ________ at school that morning when the window was broken.
A:arriving
B:arrived
C:to arrive
D:have arrived
如果最简二次根式x+2与3x是同类二次根式,那么x的值是( )
如图,一理想变压器原副线圈的匝数比为1:2;副线圈电路中接有灯泡,灯泡的额定电压为220V,额定功率为22W;原线圈电路中接有电压表和电流表.现闭合开关,灯泡正常发光.若用U和I分别表示此时电压表和电流表的读数,则( )