In the context of the input sentence, determine the relationship between 'Centrica' and 'British Gas'.
Options: brand, distribution format, owner of, headquarters location

The competition watchdog said in March that it had granted permission for British Gas Trading (BGT) - a subsidiary of Centrica (LSE: CNA.L - news ) , the UK's biggest energy supplier - and Northern Powergrid to appeal against Ofgem's price control decision.
owner of