Utilize the input text as a context reference, choose the right relationship between Banamex and Citigroup from the options. Options: product/material produced, manufacturer, distributed by, industry, position held, original broadcaster, owned by, founded by, distribution format, headquarters location, stock exchange, currency, parent organization, chief executive officer, director/manager, owner of, operator, member of, employer, chairperson, platform, subsidiary, legal form, publisher, developer, brand, business division, location of formation, creator.

Citigroup said it had opted to close Banamex USA after concluding it "has not been able to operate to the scale necessary to generate consistent quality earnings."

Answer: operator