22单选(4分)-|||-设G(x,y)有连续偏导数,积分 _(c) C(x,y)(ydx+xdy) 与路径无关,则G(x,y)应满足-|||-A. (x,y)=-y(G)_(y)(x,y)-|||-B. _(x)(x,y)=(G)_(y)(x,y)-|||-C. _(x)(x,y)=-(G)_(y)(x,y)-|||-D. (G)_(x)(x,y)=y(G)_(y)(x,y)