Utilize the input text as a context reference, choose the right relationship between grocery and Walmart 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.

Walmart is also testing an online grocery service in five cities — San Jose, Calif., Denver, Bentonville, Ark., Phoenix and Huntsville, Ala. Customers can order groceries online, then schedule a pick-up time.

Answer: operator