A:opens
B:is opened
C:will open
D:will be opened
下列说法正确的是( )
下面四个图形中,∠1与∠2是对顶角的图形的个数是( )
Jack Ripper was ________ for murdering many people in the nineteenth century.
在Rt△ABC中,∠C=90°,∠A=30°,AB=4,则AC=____