Between "The Devil and Kate" and "Martha" which has more acts?
The Devil and Kate:  112, B.201, ("Čert a Káča" in Czech) is an opera in three acts by Antonín Dvořák to a Czech libretto by Adolf Wenig. Martha (opera): Martha, oder Der Markt zu Richmond ("Martha, or The Market at Richmond") is a "romantic comic" opera in four acts by Friedrich von Flotow set to a German libretto by Friedrich Wilhelm Riese and based on a story by Jules-Henri Vernoy de Saint-Georges.
Martha