Answer the following question: SM U-21 (Germany) - SM U-21 was one of the most famous U-boats to serve in the Imperial German Navy in World War I. She was the first submarine to sink a ship with a self-propelled torpedo. She also sank the British battleships HMS Triumph and HMS Majestic. U-21 survived the war and sank while under tow by a British warship in 1919. Given a choice of categories company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work, the text refers to which one?
Answer:
Mean Of Transportation