It is completely equivalent to X, Y and Z in the two formulas of x+y+z=0.

So the integral ds of x on the curve = the integral ds of y on the curve = the integral ds of z on the curve.

And the integral on the curve (x+y+z)ds=0.

So the integral xds= the integral yds= the integral zds=0.

So the integral of (x-2y) on the curve is also 0.

The answer is B.