Utilize the input text as a context reference, choose the right relationship between ExxonMobil and Rex Tillerson 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.
Text: Major industry figures including BP chief executive Bob Dudley and ExxonMobil chief executive Rex Tillerson have warned that oil prices could be depressed for at least a few more years.
user
chief_executive_officer
assistant