Option A is Correct: The Global Environment Facility (GEF) serves as a financial mechanism for several major international environmental conventions, including the Convention on Biological Diversity (CBD) and the United Nations Framework Convention on Climate Change (UNFCCC).

Option B is Incorrect: The GEF is a financial organization that provides grants and funding for environmental projects; it is not a scientific research body. Scientific research and assessments are typically conducted by organizations like the IPCC or IPBES.

Option C is Incorrect: The GEF is an independent financial organization, not an agency under the OECD. It was established in 1991 and restructured after the 1992 Rio Earth Summit to serve as a mechanism for global environmental cooperation.

Option D is Incorrect: Since only statement A is correct, this option is false.