An experiment labels pyruvate with radioactive C at C₂, which is the middle, keto carbon. Where would this radiolabel appear after one turn of the citric acid cycle?
a) in one carboxyl group of oxaloacetate
b) equally divided between the two carboxyl groups of oxaloacetate
c) on the methylene carbon, − CH₂ , of oxaloacetate
d) as CO₂