This question is about different methods of Alternative Dispute Resolution (ADR). The key phrase is "without the intervention of a third party."
Step 1: Define the different ADR methods.
(^) Mediation: A neutral third party (the mediator) facilitates communication between the disputing parties to help them reach a voluntary settlement. The mediator does not impose a decision.
(_) Arbitration: The parties present their case to a neutral third party (the arbitrator or a panel), who acts like a private judge and makes a binding decision (an 'award').
(`) Conciliation: Similar to mediation, but the third party (conciliator) can take a more active role in suggesting potential solutions to the parties.
(a) Negotiation: The parties communicate directly with each other to try and reach a mutually acceptable agreement. There is no neutral third party involved.
Step 2: Match the definition to the method.
Since the method described involves no third party, it is by definition negotiation.