Which country entered World War I in April 1917, helping break the long stalemate on the Western Front?

Who was general manager of the Metropolitan Opera from 1950 to 1972? Brazil abolished which institution in 1888, 23 years after the United States? "Breaker, breaker" - which song by C.W. McCall topped the charts in early 1976? Which breakfast food's name can also be used as a verb meaning "to flatten completely"? Breaking a long tradition of neutrality, Denmark became a founding member of which military alliance in 1949? "Breaking up is hard to do," but on January 1, 1984, which telecommunications giant was forced to break up? What word describes how a dog breathes heavily with its mouth open after a run? Which author wrote the Uncle Remus tales, in which Brer Rabbit says he was "bred en bawn in a brier patch"?