Description for Correct answer:
Given that \( \Large x^{2}+y^{2}+2gx+2fy+c=0 \)

and \( \Large g^{2}+f^{2}=c \)

Radius of circle = \( \Large \sqrt{g^{2}+f^{2}-c} \)

\( \Large \therefore g^{2}+f^{2}=c \)

=> Radius = 0

Thus given equation represents a circle of radius 0.