Alternate exterior means opposite sides of the transversal and outside the parallel lines... angles 1, 2, 5, 6 are all outside the parallel lines.. now you just need to match up the ones that are on opposite sides... 1 and 5 are opposite sides and 2 and 6 are opposite sides.. so those two pairs are the alternate exterior angles.. since 2 and 6 isn't a choice and 1 and 5 is, then there is your answer.