All the books donated by the students from urban schools are said _____ to the students in rural areas

the other day. [ ]

A. to be sent

B. being sent

C. having been sent

D. to have been sent

有一柱形容器高5dm，底面积为100cm²，内装有3dm深的水（g取10N/kg）

（1）距离容器底5cm深处水的压强是多少？

（2）当把一个质量为0.5kg，体积为600cm³的物体投入水中平衡时，物体受到的浮力为多大？