Final answer:
The electrons excited by sunlight in Photosystem I are replaced by NADP+.
Step-by-step explanation:
The electrons excited by sunlight in Photosystem I are replaced by NADP+. During photosynthesis, Photosystem I uses the energy from sunlight to excite electrons. These excited electrons are then passed along an electron transport chain, and NADP+ acts as the final electron acceptor, capturing the electrons and becoming reduced to NADPH. This NADPH can then be used in other reactions in the process of photosynthesis.