Select the correct answer. Aubrey takes four different roads on her way to work. The speed at which Aubrey travels is indicated by segments A, B, C,
and D on the graph. Assuming Aubrey drives the speed limit on each road, which segment represents the road with the
highest speed limit?

Set $r$ is a set of rectangles such that (1) only the grid points shown here are used as vertices, (2) all sides are vertical or horizontal and (3) no two rectangles in the set are congruent. if $r$ contains the maximum possible number of rectangles given these conditions, what fraction of the rectangles in set $r$ are squares? express your answer as a common fraction.