Concept:The OPEC Conference requires a minimum attendance of member states to make its decisions valid.Explanation:OPEC’s rules state that the Conference can only hold a valid meeting when at least three-quarters of its member states are present.This condition is called a quorum.It ensures that decisions are supported by a strong majority of members, not just a few countries.Therefore, the correct requirement is three-quarters of the member states.Answer:D. three quarter of the member state