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

BlackRock Inc. and Citigroup Inc. are among the firms to have sold large bond deals backed by loans made by Prosper.

Answer: owned_by