A) The products of photosynthesis cannot be used by other organisms.
This is false. Photosynthesis produces oxygen, which then other organisms take in to produce carbon dioxide.
B) The products of respiration can be used by plants for photosynthesis.
This is true. Respiration produces CO2 (carbon dioxide), which plants take in during photosynthesis to create sugar and oxygen.
C) The exchange of oxygen and carbon dioxide occurs only in respiration.
This is false, both processes use oxygen and CO2.
D) The exchange of oxygen and carbon dioxide occurs only in photosynthesis.
This is also false.
So we know that the correct answer will be:
B) The products of respiration can be used by plants for photosynthesis.
