Citigroup Inc. on Wednesday confirmed that it will close Banamex USA, a small unit doing business across the U.S.-Mexico border, and agreed to pay $140 million to regulators who said the unit hadn’t done enough to protect itself from money launderers.
Take context from the input text and decide on the accurate relationship between 'Banamex' and 'Citigroup' from the options provided.
Options: stock exchange, parent organization, operator, publisher