Mum__________ me to school as she knew it was important for me to receive education，but we were so poor then．

A．had sent

B．sent

C．would have sent

D．would send

统计图中的圆图适用于表示（）

A.构成比

B.相对比

C.各现象的比较

D.某现象的发展速度

E.某种现象出现的频数