When we complete the square it's gonna be something like
[tex](x+C/2)^2 + (y+D/2)^2 = (C/2)^2 + (D/2)^2 - E [/tex]
So the center is [tex](-C/2, -D/2)[/tex] and the squared radius is something minus [tex]E[/tex]
When the center is constant but the radius decreases, the correct answer is C and D are unchanged but E increases. So really none of the above. I think the question writers made a mistake. But go with choice E.
