A:studied, had gone
B:had studied, went
C:has studied, goe
D:had studied, had gone
一个周角可以分成____ 直角。
如图,E、F分别是正方形ABCD的边BC、CD上的点,BE=CF,连接AE、BF.将△ABE绕正方形的对角线交点O按顺时针方向旋转到△BCF,则旋转角是( )