Answer:
Option B
Step-by-step explanation:
In an experimental study, a hypothesis is considered rhe elated to any observation and based on that observation some conclusion is devised.
To test the hypothesis, certain variable are determined and their varied in the course of experiment to study their impact on the subject of the experiment.
Here in this research, the independent variable is "either 20 or 40 milligrams of Prozac" while the subject is "individual who is clinically depressed". After the experiment, the researcher draws a conclusion i.e "the clients who took 40 milligrams of Prozac aresignificantly less depressed than those cfients who took 20 milligrams of Prozac"
Hence, option B is correct