question: Which opera has more acts, Owen Wingrave or Mireille?
answer: Mireille
context: Title: Mireille (opera)
  Passage: Mireille is an 1864 opera in five acts by Charles Gounod to a French libretto by Michel Carré after Frédéric Mistral's poem "Mireio".  The vocal score is dedicated to George V of Hanover.
  Title: Jean-Vital Jammes
  Passage: Jean-Vital Jammes (known by the stage name Ismaël) (28 April 1825 – 13 June 1893) was a French opera singer.  During a stage career spanning 40 years, he created many leading baritone roles, including Zurga in Bizet's "Les pêcheurs de perles" and Ourrias in Gounod's "Mireille".  Born in Le Passage d'Agen near the town of Agen, he was largely self-taught and made his stage debut in 1841 at the age of 16.  After singing in a several provincial theatres, he was engaged by the Théâtre Lyrique in Paris and later by the Opéra-Comique.  Following his retirement from the stage, Ismaël lived in Marseille where he died at the age of 68.
  Title: Owen Wingrave
  Passage: Owen Wingrave, Op.  85, is an opera (originally written for a televised performance) in two acts with music by Benjamin Britten.  The libretto is by Myfanwy Piper, after a short story by Henry James.
citations: Owen Wingrave Mireille (opera)