单项选择题

设f(x),g(x)在区间[a,b]上连续,且g(x)<f(x)<m,则由曲线y=g(x),y=f(x)及直线x=a,x=b所围成的平面区域绕直线y=m旋转一周所得旋转体体积为( ).

A.π∫ a b [2m一f(x)+g(x)][f(x)一g(x)]dx
B.π∫ a b [2m一f(x)一g(x)][f(x)一g(x)]dx
C.π∫ a b [m一f(x)+g(x)][f(x)一g(x)]dx
D.π∫ a b [m一f(x)一g(x)][f(x)一g(x)]dx