Which ancient Roman arena could hold around 50,000 spectators?

Which insects are sometimes called "white ants," though they are not ants at all? Which flightless bird of Mauritius had died out by about 1681? Which underwear brand's name was trademarked in 1871, making it one of the oldest U.S. trademarks? Which country gained independence from South Africa in 1990, though South Africa kept the port of Walvis Bay until 1994? Which singer wanted to play himself in a 1946 film biography but was too old, so Larry Parks got the role? Which South American country is about 2,650 miles long but averages less than 110 miles wide? The Altiplano, Spanish for "high plain," is a plateau about 12,000 feet up in which South American mountains? Which group of aluminum silicate minerals is the most abundant in Earth's crust?