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.

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.

Answer: chief_executive_officer