What is the relationship between 'Banamex' and 'Citigroup' in the context of the input sentence.
Options: founded by, operator, member of, subsidiary

Thu, Jul 23, 2015, 00:04 BST - UK Markets open in 7 hrs 56 mins Citigroup shuts Banamex USA, pays $140 mn in fines AFP – 40 minutes ago View Photo
operator