Let \( S_{1}=\left\{z_{1} \in C:\left|z_{1}-3\right|=\frac{1}{2}\right\} \) and \( S_{2}=\left\{z_{2} \in C:\left|z_{2}-\right| z_{2}+1||=\left|z_{2}+\right| z_{2}-1||\right\} \). Then, for \( z_{1} \in \) \( S_{1} \) and \( z_{2} \in S_{2} \), the least value of \( \left|z_{2}-z_{1}\right| \) is :
[Main July 28, 2022(1)]
(a) 0
(b) \( \frac{1}{2} \)
(c) \( \frac{3}{2} \)
(d) \( \frac{5}{2} \)
