The correct option for an electron carrier among the choices you provided is NAD+.
NAD+ (Nicotinamide adenine dinucleotide) is a well-known electron carrier in cellular respiration and plays a crucial role in redox reactions. It accepts electrons and is reduced to NADH, which can then donate electrons to the electron transport chain.
FAD (Flavin adenine dinucleotide) is also an electron carrier, but in the provided options, NAD+ is explicitly listed as an acceptable answer.