Which of these two act operas, Lucrezia Borgia or Il pirata, was based on a three-act melodrame? 
Lucrezia Borgia (opera): Lucrezia Borgia is a melodramatic opera in a prologue and two acts by Gaetano Donizetti. Il pirata: Il pirata ("The Pirate") is an opera in two acts by Vincenzo Bellini to an Italian libretto by Felice Romani which was based on a three-act mélodrame from 1826, "Bertram, ou le Pirate" ("Bertram, or The Pirate") by Charles Nodier and "Raimonde" (actually Isidore Justin Séverin Taylor).
Il pirata