若 :(x)^2+(y)^2=(R)^2 ,其中R-|||-则下列正确的是 ()-|||-bigcirc A. (int )_(I)^-((x)^2+(y)^2)ds=pi (R)^3-|||-bigcirc B. (int )_(L)^-(x)^2ydslt 0-|||-C. (int )_(L)^-(L)^-2-(d)^2yds=0-|||-bigcirc D. (int )_(I)^2((x)^2+(y)^2)ds=pi (R)^2