Step 1: Understanding the composition of functions.
We are tasked with finding \( f \circ f \), which means applying the function \( f(x) \) to itself. This requires substituting \( f(x) \) into itself. The function \( f(x) \) is given by:
\[ f(x) = \frac{2x + 3}{3x - 2} \]
Step 2: Substituting \( f(x) \) into itself.
We compute \( f(f(x)) \) by substituting \( f(x) \) into the formula for \( f(x) \):
\[
f(f(x)) = f\left( \frac{2x + 3}{3x - 2} \right)
\]
This results in an identity function because applying \( f \) to itself yields the original input.
Step 3: Conclusion.
Therefore, \( f \circ f \) is an identity function, which makes option (B) the correct answer.