Two neighboring countries are in a dispute over the condition of a river which is common to both. Each country believes that the other country is polluting the river to dangerous levels. To resolve the situation, they decide to use a method of alternative dispute resolution (ADR) that is particularly useful in resolution of environmental disputes, and they voluntarily appoint a neutral third party. This method of dispute resolution is referred to as _____.

A) minitrial

B) summary jury trial

C) litigation

D) mediation