The midpoint of the line segment is the average of the respective coordinates.
So the x-value of the midpoint if the average of the two individual x-coordinates.
(-3.5 + 4)/2 = 0.5/2 = 0.25
And the y-value of the midpoint if the average of the two individual y-coordinates.
(2 + (-2.5))/2 = -0.5/2 = -0.25
So, the midpoint is (0.25, -0.25) or (1/4, -1/4) or "C".
