I believe the answer is A or C
Oxygen and glucose at top
carbon dioxide and water at bottom
Cogeneration is the process of taking a waste product or process and producing heat and generating electricity from it at the same time.
It could be collection of waste heat from the original generation of electricity or burning of biodiesel, ethanol or methane gas from sewer or cow dung. The only answer where electricity is using or creating heat and generating electricity power is C.