Please answer the following question: British Rail Class 309 -  The British Rail Class 309 Clacton Express electric multiple units (EMUs) were built by British Rail (BR) York Works from 1962-1963. They were initially classified as Class AM9 before the introduction of TOPS. These units were the first express 25 kV alternating current (AC) units to be built by British Rail and British Rail's first EMUs to be capable of 100 mph. 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