In an experiment,participants are randomly assigned to different levels of the:

A) independent variable.
B) dependent variable.
C) independent and dependent variables.
D) third variable.

Random assignment is used to ensure that participants have an equal chance of being selected for each level of the independent variable. This helps control for any potential confounding variables and increases the internal validity of the study. The dependent variable is measured, not manipulated or assigned, so it does not make sense to randomly assign participants to different levels of the dependent variable. The term "third variable" typically refers to a potential confounding variable, which is not something that is assigned to participants.