The circle $a z \bar{z}+g(z+\bar{z})-i f(z-\bar{z})+c=0$, where $a, c \neq 0$ is mapped into
(a) a circle in the $w$ - plane, which does not pass through the origin
(b) a circle in the $w$ plane passing through the origin
(c) a straight line through the origin
(d) a straight line not through the origin