A:where
B:that
C:which
D:whe
一个圆锥的母线长是底面半径的2倍,则侧面展开图扇形的圆心角是( )
如图,AC为入射光线,CB为折射光线,且AO<OB.已知AO=10cm,该凸透镜的焦距可能是( )
I fell off my bike and hurted my leg. ____