Called Earth's twin, which planet's surface is hidden by thick clouds of sulfuric acid?

Harvard's Widener Library, opened in 1915, was built in memory of a victim of which tragedy? Cast in 1586, the world's largest cannon by caliber stands in which Moscow landmark? Which American author, whose surname sounds like the German word for "Sunday," wrote the novel "The Volcano Lover"? In which city is the ballet "Graduation Ball" set, as cadets attend a dance at a girls' school? In which Jules Verne novel does Captain Nemo finally die, revealing that he is an Indian prince? Caribbean cooks use which fruit to marinate chicken and beef, since its enzyme papain tenderizes meat? Cubby O'Brien, Karen Pendleton and Annette Funicello were among the original cast members known as what? Which Pittsburgh banker served as U.S. treasury secretary under three presidents and founded the National Gallery of Ar…