1.设C为从A(0,0)到B(4,3)的直线段,则 (int )_(c)^2(x-y)ds= ()-|||-A. (int )_(0)^4(x-dfrac (3)(4)x)dx B. (int )_(0)^3(dfrac (4)(3)y-y)dy-|||-C. (int )_(0)^3(dfrac (4)(3)y-y)sqrt (1+dfrac {9)(16)}dy D. (int )_(0)^4(x-dfrac (3)(4)x)sqrt (1+dfrac {9)(16)}dx