Answer:
The correct answer will be option-B.
Step-by-step explanation:
The scientific experiments are performed to study the hypothesis and prove it. The scientific factor to be studied in the experiment are known as the "variables". The variables can be "independent variables" which can control and changed, "dependent variables" which remains constant and to be studied and control variables which are kept constant in the experiment.
In the given question, the experiment is performed to study the effect of "loud noise" on the growth of plants so the dependent variable is plant growth dependent on loud noise. Since the same amount of water is provided to each plant will be a controlled variable.
Thus, Option-B is the correct answer.