Answer:
D. experimental method
Step-by-step explanation:
Experimental method: In psychological research, the term "experimental method" is described as one of the different research methods in which one variable is being manipulated in order to determine whether changes or alteration in one variable leads to create changes in the other variable. However, experimental methods rely on the random assignment, controlled methods and the alteration of variables in order to test a "hypothesis".
In the question above, the given statement represents the experimental method.