Answer:
your answer is c
Explanation:
i dont know how to explain
It is true that in the science laboratory setting, scientists often struggle to achieve valid results. A possible solution for this dilemma is to repeat the procedure for several trials.
Simple answer is that the plants are conducting more photosynthesis than all the organisms in the tank are carrying out cellular respiration. This would be why the carbon (CO2) levels are decreasing. They are being incorporated into the plant as sugars.