Respuesta :
Answer:
Option B
Explanation:
When Bromthymol blue (BTB) receives carbon dioxide (after a student exhales into it), turns yellow. This yellow color is due to the formation of slightly acidic carbonic acid. Now, an aquatic green plant is placed in both the test tubes and one of these test tube is placed in sunlight. Thus, the test tube kept in sun has all ideal requirements that would allow the plant to photosynthesize. Photosynthesis process removes carbon dioxide from the test tube and hence it apperas blue again. While the test tube in dark still appears yellow in color
Hence, option B is correct