Utilize the input text as a context reference, choose the right relationship between TD Ameritrade and public company 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.

The catalyst for TD Ameritrade was really our public company clients, right?

Answer: legal_form