Utilize the input text as a context reference, choose the right relationship between Sheryl Sandberg and chief operating officer 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.

MOBILE BOWL : Sheryl Sandberg , chief operating officer at Facebook, took to the Advertising Week stage on Tuesday to champion mobile advertising’s ability to reach a big audience with targeted ads, CMO Today reports.

Answer: position_held