carbon dioxide (CO2) and hydrogen (H2) oxygen (O2) and carbon dioxide (CO2) carbon dioxide (CO2) and water (H2O) oxygen (O2) and water (H2O)
I gave my students this multiple choice question: During photosynthesis, plants absorb light energy from the Sun and convert it into chemical energy in the form of glucose. Which compounds combine in the presence of sunlight to form glucose?

Only one answer is correct among these 4 choices:
- carbon dioxide (CO2) and hydrogen (H2)
- oxygen (O2) and carbon dioxide (CO2)
- carbon dioxide (CO2) and water (H2O)
- oxygen (O2) and water (H2O)

Could you tell me which one is correct?

carbon dioxide (CO2) and water (H2O)