In glycolysis, ATP is formed by the transfer of a high-energy phosphate from 1,3-bisphosphoglycerate to ADR No such high-energy phosphate donor has ever been isolated in mitochondria because

• A. no such phosphate donor exists
• B. the techniques for isolating the phosphate donor are not refined enough
• C. None of the above
• D. the high-energy phosphate donor is very short-lived and difficult to isolate