The molecule which is the final electron acceptor for electrons from photosystem I is (d) NADP⁺.
Photosystem I is the protein complex involved in the process of photosynthesis. It captures the light energy to mediate the transfer of electrons from a series of electron transporters. It is involved in non-cyclic as well as cyclic photophosphorylation.
NADP⁺ is the Nicotinamide Adenine Dinucleotide Phosphate. It acts as a coenzyme. It is an important constituent in various anabolic reactions like Calvin cycle, lipid and nucleic acid syntheses, etc. The oxidized form of NADP⁺ is NADPH. It is present in organisms of almost all kinds.
Complex molecules are made up of other elements bonded with carbon. Carbon is able to bond with other molecules so easily because it has four valence electrons.