Which graph matches y=x?

Answer:
see below
Step-by-step explanation:
Of your remaining answer choices, the only one that shows a reflection (not a translation) is the one below. It has the orientation of the figure reversed (side lengths shortest-to-longest are CCW instead of CW).
The reflection over y=x reverses the coordinates: (x, y) ⇒ (y, x), so the vertices become ...