What is the fourth step to convert a logical network to all NOR gates?

Use double inversion to complement outputs of AND gates.

Use double inversion to complement inputs of $OR$ gates.

Apply DeMorgan's theorem to replace OR gates with NAND gates.

Utilize NAND gates instead of NOT gates to complement necessary inputs and outputs.

Use double inversion to complement outputs of OR gates.

Use double inversion to complement inputs of AND gates.

Apply DeMorgan's theorem to replace AND gates with NOR gates.

Utilize NOR gates instead of NOT gates to complement necessary inputs and outputs.

None of these answers.