In this experiment setup, the objective is to find out the rate of photosynthesis with changing temperature. It has provided the conditions for photosynthesis to happen which is light, air, water and chlorophyll plus the heating element to vary the temperature for observation of the process changes, if any.
However, there is no measurement of the outcome set to determine how to get the results that you want.
How can we tell if they are performing photosynthesis? One way is to see if they are giving off oxygen, one of the by-product of photosynthesis.
By right, using a water plant, you would be able to see bubbles being formed when oxygen is given off. However, our eyes cannot quantify the water bubbles accurately, so if there is an oxygen sensor to do that, the experiment results will be more accurate.
Hence (4) is the best answer. (2) and (3) is totally out. (1) is possible but still not a definite result based on eye observation.