A student poured a solution of bromthymol blue indicator into three test tubes. Then, he placed an aquatic plant in two of the test tubes. He placed a stopper on each test tube and placed them all in the dark for 24 hours. Bromthymol blue turns from blue to yellow in the Presence of CO2. Please help me before I fail

Question 1 - Which process or processes would you expect the organisms in the test tubes to carry out? Cellular Respiration, photosynthesis or both?

Question 2 - What is the purpose of the bromthymol blue in the experiment? How can the student use this indicator to draw conclusions about the processes that the aquatic plants are carrying out?

Question 3 - Predict what colour the test tubes will be 24 hours in the dark?

Question 4 - The student takes test tube 3 (after it has been in the dark for 24 hours) and out it in a sunny window, predict what will happen to the colour of the test tube. Give reasoning to support your prediction.