Answer:
A) The aim of the experiment is to test the plant for photosynthesis.
B) Sodium hydrogen carbonate is known to increase the amount of carbon dioxide supply to the plants. Hence, it the availability of sodium hydrogen carbonate ensures that carbon dioxide is not the limiting factor for the experiment.
C) Submerged water plants are used because using these plants makes it easier to measure the rate of photosynthesis. Water and carbon dioxide become readily available to the plant which are the reactants for photosynthesis.