Hello there!
The center of any circle is the midpoint of the diameter.
Let's use the midpoint formula to find the midpoint of the diameter.
The midpoint of a line segments with endpoints [tex](x_1, y_2)[/tex] and [tex](x_2, y_2)[/tex] will have a midpoint of [tex]( \dfrac{x_1+x_2}{2}, \dfrac{y_1+y_2}{2})[/tex]
Midpoint of the diameter:
[tex]( \dfrac{-3-11}{2}, \dfrac{-5-7}{2})[/tex]
[tex]=(-7, -6)[/tex]
Your answer is B. Hope this helps!
