Answer:
Midpoint of a line segment with the endpoints A(a1, a2), B(b1, b2) is M(1/2*(a1 + b1), 1/2*(a2 + b2))
So,
(1/2*(-4 + 7), 1/2*(-3 + (-5))) = (1/2*3, 1/2*(-8)) = (1.5, -4)
Answer D is correct.
Commen factor means you can get integers after division.
A. 20 is not correct
B. Correct
C. Correct
D. 56 is not correct