设函数f(x，y)连续，则∫12dx∫x2f(x,y)dy+∫12dy∫y4-yf(x,y)dx=( ). A: ∫12dx∫14-xf(x,y)dy． B: ∫12dx∫x4-xf(x,y)dy C: ∫12dx∫14-yf(x,y)dy． D: ∫12dx∫yyf(x,y)dy
设函数f(x，y)连续，则∫12dx∫x2f(x,y)dy+∫12dy∫y4-yf(x,y)dx=( ). A: ∫12dx∫14-xf(x,y)dy． B: ∫12dx∫x4-xf(x,y)dy C: ∫12dx∫14-yf(x,y)dy． D: ∫12dx∫yyf(x,y)dy
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