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. Rubis-class submarine - The Rubis type is a class of first-generation nuclear attack submarines of the French Navy. They are the most compact nuclear attack submarines to date. All submarines of the class (except for Casabianca) are named after gemstones.
The answer to this question is:
Mean Of Transportation