某矿精煤灰分要求≤13%，精煤分选密度为1.8，一批精煤样品在浮沉后，浮物灰分为13.1%，说明()。

A.分选密度不合适，需向下调

B.分选密度不合适，需向上调

C.工作参数正常，不用作任何调整

D.灰分差别很小，不调整也疫关系

The inside dimensions of a rectangular wooden box are 6 inches by 8 inches by 10 inches. A cylindrical cannister is to be placed inside the box so that it stands upright when the closed box rests on one of its six faces. Of all such cannisters that could be used, what is the radius, in inches, of the one that has maximum volume ？（）

A．3

B．4

C．5

D．6

E．8