Find all points on the curve y$+$x$=$x$2+$y$2$y$+$x$=$x$2+$y$2$where the tangent line is horizontal.

Select one:

a$.$

$(0,0)(0,0)$

b$.$

$(12,1+22)(12,1+22)$ and$(12,122)(12,122)$

c$.$

$(12,1+22)(12,1+22)$ and$(12,122)(12,122)$

d$.$

None of the above