Many researchers devise "sham" treatments for their control groups to undergo, meaning that the control group interacts with researchers in some way that is not thought to impact the dependent variable or the outcome. This is done to weaken the argument that the treatment group improvement may have occurred in part simply due to the attention this group received from the researchers.
1. These researchers are attempting to control for which of the following?
a. multiple treatment interference
b. the Hawthorne effect
c. selection
d. experimenter effects

b. the Hawthorne effect                                                

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".

a would be the answer