Members of opec
a. only allow one new member per year
b. share oil only amongst other opec members
c. hold over half of the world's oil
d. hold about 40% of the world's oil

  D. Hold about 40% of the world´s oil

Explanation:

  OPEC is the acronym for Organization of the Petroleum Exporting Countries. It is an intergovernmental organization of 14 countries founded in 1960. These nations had approximately 44% of the global oil production and 81.5% of the world´s estimated oil reserves. The OPEC had a major influence on oil prices.

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