Step 1: Understand the logic of the circuit.
The symbolic form of the circuit represents the logic gates for switches \( s_1, s_2, s_3 \), which are closed when the respective switches are true. By analyzing the circuit and simplifying the expressions for the states of the switches, we arrive at the correct logical expression for the circuit.
Step 2: Conclusion.
The correct symbolic form is \( (p \wedge q) \vee [\neg p \wedge (\neg q \vee p \vee r)] \equiv \ell \), corresponding to option (C).