A certain grocery purchased x pounds of produce for p dollars per pound. If y pounds of the produce had to be discarded due to spoilage and the grocery sold the rest for s dollars per pound, which of the following represents the gross profit on the sale of the produce ？（）

A.（x-y）s-xp

B.（x-y）p-ys

C.（s-p）y-xp

D.xp-ys

E.（x-y）（s-p）

大网膜的作用及特性有（）。

A.活动度大

B.可移动性

C.可移动到病灶处

D.有包裹、填塞病灶作用

E.因有丰富血管，故可作外科材料