Compare with the standard form of equation of a circle
(x - a)^2 + (y - b)^2 = r^2 where the center is at (a,b) and radius = r:-
(x - 9)^2 + (y + 8)^2 = 16
r^1 = 16 giving the radius = 4 That is a diameter of 8.
and center is at ( 9 , -8)
Correct choice is b.