A. Photosynthesis removed carbon dioxide from the water.
Explanation - Photosynthesis is the process that uses carbon dioxide [tex]CO_{2}[/tex], water [tex](H_{2}O)[/tex], sunlight and chlorophyll to make glucose or food. When the process of photosynthesis is performed in the test tube, then [tex]CO_{2}[/tex] is absorbed from the water.
[tex]CO_{2}[/tex] makes its way through the stomata present on the leaves of the plant. Thus, the pH of water inside the test tube changes. In plants, photosynthesis takes place inside the grana of the chloroplast. This process involves light dependent and light independent reaction.
