[HDLBits]

This is a combinational circuit. Read the simulation waveforms to determine what the circuit does, then implement it.

---

According to waveforms we can gain the truth table

so that we can easy find logic in the circuit.

---

module top_module (
    input a,
    input b,
    input c,
    input d,
    output q );//

    assign q = b | c; // Fix me

endmodule