如图,△AOB中,∠AOB=90°,AO=2,BO=4,△AOB绕顶点O逆时针旋转到△A′OB′处,此时线段A′B′与BO的交点E为BO的中点,则线段B′E的长度为____
观察图形,阴影部分表示四种植物的共同特征,这一特征是( )
A. It's time for Chinese class. B. It's time for lunch.
C. It's time for school. D. Time to go home.
____