The correct option is A.
In scientific investigation, variable refers to those parameters that are manipulated or changed in an experiment. Variables are those factors or conditions that can exist in different amounts in a scientific investigation. There are three major types of experimental variables, these are, independent, dependent and controlled variables. All the variables that are used in an experiment are usually connected to one another, scientific investigators typically look for the relationships among the variables in order to depict how they associate with one another.
