The questions provide a list of substances involved in photosynthesis, some are products and some are inputs.
Let's take a look at the photosynthesis equation. On the left, there are the reactants and on the right , anproducts:d in thethe
We can see that on the left side there is carbon dioxide and water, and that light is over the arrow, indicating that is needed for the reaction to occur.
So, the three inputs of photosynthesis are carbon dioxide (b), light (c), and water (f).