Which statement is true? a. the graph of a two-variable equation is the set of all points in the coordinate plane that solve the equation. b.the graph of a two-variable equation consists of only two points: one with a zero y-coordinate, (a,0), and one with a zero x-coordinate, (0,b).c. the graph of a two-variable equation is the set of all positive points that solve the equation. d.the graph of a two-variable equation is a single point that solves the equation.