Answer:
Carbon dioxide is required for process of photosynthesis.
Explanation:
Photosynthesis is the process that fixes carbon dioxide into glucose in the presence of sunlight. The excess of glucose is stored in form of starch in plants. Unavailability of carbon dioxide to plant 2 (due to the presence of soda lime in the bag that absorbed it) did not allow the photosynthesis to occur leading to the absence of starch in this plant. The experiment confirms that carbon dioxide is required for the process of photosynthesis to occur.