The three reactants needed for
photosynthesis are
and

Light energy, Water, and Carbon Dioxide/Chlorophyll

Explanation:

Photosynthesis uses 12 water molecules, 6 Carbin Dioxide molecules and light energy so it can produce one glucose, six water and oxygen molecules. This can be expressed and represented by 12H2O + 6CO2 + light energy = C6H12O6 + 6H2O + 6O2

Vital to remember that the produced oxygen is from the original water molecules and not the carbon dioxide.

b is the correct answer