Let \( S_1 = \{\, z_1 \in \mathbb{C} : |z_1 - 3| = \dfrac{1}{2} \,\} \) and \( S_2 = \{\, z_2 \in \mathbb{C} : |z_2 - |z_2 + 1|| = |z_2 + |z_2 - 1|| \,\} \). Then, for \( z_1 \in S_1 \) and \( z_2 \in S_2 \), the least value of \( |z_2 - z_1| \) is:
\( 0 \)
\( \dfrac{1}{2} \)
\( \dfrac{3}{2} \)
\( \dfrac{5}{2} \)
