Final answer:
In a research experiment, controlling for unwanted variability helps minimize the influence of confounding variables.
Step-by-step explanation:
In a research experiment, experimenters control for unwanted variability in factors such as age, gender, ethnic background, socioeconomic status, etc. to minimize the influence of confounding variables.
Confounding variables are additional variables that can cloud the study and affect the results. By controlling these factors, researchers can more accurately determine the relationship between the independent variable and the dependent variable.
Therefore, the correct answer is b) Confounding variables.