在Rt△ABC中,∠C=90°,AB=10.若以点C为圆心,CB为半径的圆恰好经过AB的中点D,则AC=( )
A:5
B:52
C:53
D:6
The king ordered his men to bring all the gold here.
下列现象中,由于光的直线传播形成的是( )