Under Article 78, what must happen before a petition can be heard?

The correct choice emphasizes the requirement for due process before a court can entertain an Article 78 petition. Specifically, it mandates that the party initiating the petition must provide notice to all opposing parties at least 20 days prior to the hearing. This notice requirement ensures that all those potentially affected by the petition have an opportunity to prepare and respond, thus upholding principles of fairness and transparency in legal proceedings.

The other options do not align with the procedural rules governing Article 78 proceedings. Mediation is not a prerequisite for such petitions, as they typically involve a review of administrative actions rather than mediation between parties. The submission of an affidavit by the opposing party is not a general requirement for the hearing of an Article 78 petition, and while affidavits may be presented during the proceedings, they’re not a necessary step before a hearing. The selection of a jury is irrelevant in the context of Article 78, which deals with administrative law and does not involve jury trials. These contexts highlight why the requirement for serving notice is key to the Article 78 process.