Answer:
Step-by-step explanation:
The starting substances in photosynthesis are water and carbon dioxide, which can be represented by option A.
Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy in the form of glucose. This process takes place in the chloroplasts of plant cells. During photosynthesis, plants use water and carbon dioxide to produce glucose and oxygen.
Water (H2O) is absorbed by the plant's roots from the soil and transported to the leaves through specialized tissues called xylem. Carbon dioxide (CO2) is obtained from the air through tiny pores called stomata on the surface of leaves.
In the presence of sunlight and the green pigment called chlorophyll, the water molecules are split into hydrogen (H) and oxygen (O) atoms through a process called photolysis. The oxygen atoms are released as a byproduct, while the hydrogen atoms are used in the next step.
Simultaneously, the carbon dioxide molecules in the air enter the leaf and diffuse into the cells of the plant. In the chloroplasts, the carbon dioxide molecules combine with the hydrogen atoms from water to form glucose (C6H12O6), which is a sugar molecule and a source of stored energy.
So, in summary, during photosynthesis, the starting substances are water and carbon dioxide (option A), and the products are glucose and oxygen.
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