Carla drew a diagram to compare the roles of oxygen and hydrogen in photosynthesis.

which label belongs in the area marked y?

a-enters plant as part of water
b-combines with carbon dioxide
c-is released into air through stomata
d-is stored in leaves for later use

Option A, Enters plant as part of water

Explanation:

In the process of photosynthesis, water molecule is broken down into oxygen and hydrogen through photolysis.

Once the molecule is broken down , oxygen is  released and hydrogen ion are used for initiating the further reactions in photosynthesis.

The following reaction occurs in photolysis-

2H2O > 4H+ + O2

The image in the question shows a subset that has both hydrogen and oxygen. Therefore, water is the most suitable subset among all.

Hence, option A is correct