What is the relationship between 'Kinder Morgan' and 'Houston' in the context of the input sentence.
Options: operator, employer, headquarters location, location of formation

June-August 2014 - FERC seeks data on Houston Ship Channel and other gas sales from several companies, including units of McGraw Hill, IntercontinentalExchange, BP, Energy Transfer (Stuttgart: 4ETA.SG - news ) Partners (Other OTC: PGPHF - news ) , Enbridge (Toronto: ENB.TO - news ) , Enterprise Products, Kinder Morgan (NYSE: KMI - news ) , Atmos Energy, Castleton Commodities, Tenaska, Integrys, Encana, Exelon, Chesapeake Energy (Other OTC: CHKDJ - news ) , Chevron (Swiss: CVX.SW - news ) , Enable Energy, Barclays (LSE: BARC.L - news ) and Total (Swiss: FP.SW - news ) .
headquarters location