Pigments in photosystem 1 use energy from light to reenergize the electrons.
I would say C but I’m not too sure.
Answer: <u><em>D. An observation that has a number associated with it</em></u>
Explanation: The answer is D. An observation that has a number associated with it. I would explain further, but it is pretty self explanatory.
<em>Good luck!</em>