Answer:
a) nad+
Explanation:
Both NAD+ and FAD as electron acceptor in the Kreb Cycle, but every turn of the citric acid cycle releases two carbon dioxide molecules and consumes three NAD+ to give three molecules NADH (in three different steps) but also consumes one FAD to produce one molecule FADH2 (in one single step).
Each NAD+ accepts one electron, while each FAD accepts two electrons.
Thus, NAD+ accepts three electrons in total per cycle while FAD accepts two electrons in total per cycle.