Because of large reserves that center around the Persian Gulf, the Middle East often produces as much as two-thirds of the world’s supply of __________.

The Persian Gulf region contains some of the world’s largest reserves of petroleum, also called crude oil. Its major oil-producing countries contribute a large share of global petroleum supplies, so petroleum is the best answer. Water, cattle, and coal do not fit the reference to these reserves.

AI-written and checked against the verified answer.