Utilize the input text as a context reference, choose the right relationship between Buick and General Motors 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 United Auto Workers union blasted General Motors Tuesday for considering selling Chinese-built Buick Envisions in the United States and vowed to try to kill the plan during ongoing contract negotiations.

Answer: parent_organization