If two lines overlap completely on a graph, which statement is correct?

Correct answer: They have infinitely many solutions

The direct answer is C: infinitely many solutions. If two graphs overlap completely, they are coincident lines, meaning they are actually the same line. Every point on that line belongs to both graphs and makes both equations true. Since a straight line contains infinitely many points, the pair has infinitely many common solutions. A is wrong because no solution describes distinct parallel lines that never meet. B is wrong because exactly one solution describes two distinct intersecting lines meeting at one point. C is correct because complete overlap gives every point as a common solution. D is wrong because perpendicular lines meet at a right angle and do not overlap completely. For example, if one point on the common line is a solution, there are endlessly many other points on the same line as well. Do not count the visible drawing as one line and assume one solution; the important fact is that all its points satisfy both equations. Memory cue: overlap means identical equations geometrically, so the answer is infinitely many, not one.