Answer:
B. The researchers may be concerned with confounding that occurs when the effects of two or more explanatory variables are not separated or when there are some explanatory variables that were not considered in a study, but that affect the value of the response variable.
Step-by-step explanation:
The main concern of the researchers in this example is that their research might not properly identify a confounding variable that is present in the research. In this example, the researchers appear to be concerned with confounding. A confounding variable is one that influences both the dependent and the independent variable. This can lead to problems such as a spurious association or confounding bias.