Consider the following two subsets of $\mathbb{C}$ : $$A=\{\frac{1}{z}:|z|=2\}\text{ and }B=\{\frac{1}{z}:|z-1|=2\}\text{ . }$$ Then $$ (a) $A$ is a circle, but $B$ is not a circle. $$ (b) $B$ is a circle, but $A$ is not a circle. $$ (c) $A$ and $B$ are both circles. $$ (d) Neither $A$ nor $B$ is a circle.