Answer:
The correct answer is - oxygen.
Explanation:
The experiment of a test tube and elodea plant in which a plant of elodea is placed in a test tube filled with water and exposed to the sunlight and one is placed in the dark. The plant that is exposed to the sunlight starts forming a gas that can be seen as bubbles in the test tube.
This experiment shows the process of photosynthesis that converts sunlight into glucose with the help of carbon dioxide and water and produces oxygen as a byproduct that releases from the plants.
Thus, the gas that forms in the test tube in the form of bubble is oxygen which is released in the process of photosynthesis.
