Answer: Choice D. Segment GN is a median
A median is a segment that goes from a triangle vertex to the midpoint of the opposite side. In this case, point G is the vertex and point N is the midpoint (of side FH). Check out the visual diagram attached below.
note: I'm assuming your teacher meant to say "midpoint of FH" instead of "midpoint of FR" because point R isn't mentioned at all in triangle FGH.
