Q:Pick one category for the following text. The options are - company, educational institution, artist, athlete, office holder, mean of transportation, building, natural place, village, animal, plant, album, film or written work. United States Porpoise-class submarine - The Porpoise class were submarines built for the United States Navy in the late 1930s and incorporated a number of modern features that would make them the basis for subsequent Salmon Sargo Tambor Gato Balao and Tench classes. Based on the Cachalots enlarged to incorporate additional main diesels and generators the Portsmouth boats were all riveted.In general they were around 300 feet (91 m) long and diesel-electric powered.
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Mean Of Transportation