Which of these U.S. states is officially called a commonwealth?

Which of these was one of the four original U.S. cabinet posts under George Washington? Which dentist fought alongside the Earp brothers against the Clanton gang at the O.K. Corral on October 26, 1881? Which of these was one of the four original provinces of Canada at Confederation in 1867? In the complete metamorphosis of most insects, which stage comes between the larva and the adult? In 1903, which of these cities had both a National League and an American League team? Which of these countries borders Argentina? Which automaker joined General Motors and Ford as Detroit's "Big Three"? In 1990, the U.S. Postal Service issued stamps honoring four classic films from 1939. Which of these was one of them?