A 1920s hit by Sammy Fain and Irving Kahal said to "Let a" what "be your umbrella"?

Robert Frost's 1920 poem begins "Some say the world will end in" what, "Some say in ice"? Which name is shared by a 1920s dance and a city in South Carolina? Which Verdi opera, set in ancient Egypt, premiered in Cairo in 1871? Which 1927 Jerome Kern musical follows performers on a Mississippi River boat? Watching fish freeze solid in Labrador inspired Clarence Birdseye's method of preserving food by what? The question "Will it play in ___?", about which Illinois city, became a test of mainstream American appeal? A 1921 poem by Vachel Lindsay was "In Praise of" which wandering planter? A 1921 treaty dividing an island, with an oath of fidelity to the Crown, led to civil war in which country?