单项选择题
A.自定义放映B.当前幻灯片C.选定幻灯片
A.3~5VB.7~9VC.12~14V
A.C1y1+C2y2+y3B.C1(y1-y2)+C2(y1-y3)C.C1(y1-y2)+C2(y1-y3)+y3D.C1(y1+y2)+C2(y1+y3)+y3