Which of the following describes a variable that can be affected by another variable?

The option that describes a variable that can be affected by another variable is the dependent variable. In experiments, researchers manipulate one or more independent variables to observe how they influence the dependent variable. This relationship shows that the dependent variable's value will change in response to variations in the independent variable. For example, if an experiment is set up to test the effect of temperature on the rate of a chemical reaction, the temperature is the independent variable, while the rate of the reaction is the dependent variable, as it relies on the changes made to the temperature.

The other options serve different roles in an experimental setup. The independent variable is the factor that the experimenter changes intentionally, while control variables are kept constant to prevent them from influencing the outcome. Constants are specific values that remain unchanged throughout the experiment. In essence, the dependent variable is specifically designed to respond, making it the correct choice in this scenario.