-3 and 1/3 would be the correct answer. Rise/run. If you count, since its on a graph, one of them is 2/6 which reduces down to 1/3 positive slope. Then the other is -3/1 which reduces down to -3 slope.
rectangles are made up of 4 right angles, which means that a side and a base meet perpendicular to one another. their slopes then have to reflect perpendicular slopes. perpendicular slopes are opposite reciprocals of one another. for example, if the slope of one line is +2/3, then the perpendicular slope to that would be -3/2. so we look for that combination in our choices.
all of them satisfy that condition (so what's the question, i guess? )