The correct answer is - A) the operation of OPEC.
The Middle East is in general focused and specialized for production of oil and oil products. All of the countries in this region that are specialized in this sector are members of OPEC, and are all very influential members, through which they are also very influential on the global oil market.
OPEC is an organization created by the countries that have big oil reserves, and its purpose is that they all go on the market as a unit, in the sense of creating the prices of the oil in accordance to the conditions, and also their interests.