Acetyl-CoA labeled with 14C in both of its acetate carbon atoms is incubated with unlabeled oxaloacetate and a crude tissue preparation capable of carrying out the reactions of the citric acid cycle. After one turn of the TCA cycle, oxaloacetate would have 14C in:
a. all four carbon atoms.
b. no pattern that is predictable from the information provided.
c. none of its carbon atoms.
d. the keto carbon and one of the carboxyl carbons.
e. the two carboxyl carbons.