Answer:
b. the Hawthorne effect
Step-by-step explanation:
Hawthorne effect: In psychology, the term "Hawthorne effect" was proposed by one of the famous researcher named Henry A. Landsberger during the 1950s, and is described as the propensity of a few individuals to perform better and work more or harder when they are being allotted as participants or subjects in a particular experiment. Therefore, the behavior of these participants is being changed because of the attention they receive from their researcher instead of any manipulation in the experiment's dependent variable.
In the question above, the given statement signifies "the Hawthorne effect".