Utilize the input text as a context reference, choose the right relationship between Citigroup and Financial Services 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.

Capital One Financial Corp Discover Financial Services Bank of America Corp American Express Co Citigroup Inc

Answer: industry