She likes playing ______. [ ]
A. basketball
B. the basketball
C. the piano
D. A and C
答案:D
如图是一正弦式交变电流的电压图象.从图象可知电压的最大值和频率分别为( )
A.10V,0.02s
B.10V,50Hz
C.102V,0.02s
D.102V,50Hz
请把下边的人体器官与右边的系统用线连起来: