Explanation:
Novation refers to the substitution of an existing contract or obligation with a new one that involves new parties, rights, or duties. It involves the agreement of all parties involved in the original contract as well as the new one. Therefore, mutual consent is necessary for novation to take place.

Option A: Mutual agreement refers to the meeting of the minds between two or more parties regarding the terms of a contract. While it is important in contract formation, it is not specific to novation.

Option B: Mutual consent refers to the agreement of all parties involved in a contract or transaction. It is necessary for novation to take place because it involves the agreement of both the original parties and the new parties to substitute the existing obligation with a new one.

Option C: Free consent refers to the voluntary agreement of parties without any undue influence or coercion. While it is important in contract formation, it is not specific to novation.

Option D: None is not the correct option because novation requires the agreement and consent of all parties involved.

Conclusion: In conclusion, novation requires mutual consent because it involves the substitution of an existing obligation with a new one that involves new parties, rights, or duties. All parties involved in the original contract and the new one must agree and consent to the novation.