Meerkats live together in groups to help raise and protect their offspring. Meerkat pups are most vulnerable when they are away from their burrow foraging for food. Adult meerkats exhibit sentinel behavior, standing upright and making alarm calls to warn other members in the group that predators are nearby. In a study of meerkat behaviors, scientists observed meerkat foraging groups and recorded the presence or absence of pups along with the frequency of adult sentinel behavior. The scientists determined that sentinel behavior increased when pups were present in the foraging group. Which of the following correctly identifies the dependent and independent variables in the described study? A. The frequency of sentinel behavior is the independent variable, and the presence of pups is the dependent variable. B. The presence of pups is the independent variable, and the frequency of sentinel behavior is the dependent variable. C. The number of predators is the independent variable, and the presence of pups is the dependent variable. D. The distance from the burrow is the independent variable, and the number of predators is the dependent variable.