Please answer the following question: HMS H21 was a British H class submarine built by Vickers Limited Barrow-in-Furness as the first of the Batch 3 H class submarines. She was laid down on 20 October 1917 and was commissioned on 28 January 1918.H21 was an improved design of the H class which produced a larger displacement and the latest 21 inch torpedo tubes replacing the old 18 inch torpedo tubes. This would be incorporated into all batch 3 H class submarines.HMS H21 was sold on 13 July 1926 at Newport. Given a list of categories: company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work, what category does the paragraph belong to?
Answer:
Mean Of Transportation