The correct option is
A Median
Median is a line from a vertex to the midpoint of its opposite side.
As you can see in the given triangle,
E is the midpoint of side BC and A is connected to E by the line AE.
So, AE is the median from vertex A to side BC.
F is the midpoint of side AC and B is connected to F by the line BF.
So, BF is the median from vertex B to side AC.
D is the midpoint of side AB and C is connected to D by the line CD.
So, CD is the median from vertex C to side AB.