What percentage of children in developing countries are malnourished?

Once you have established a problem that can be studied empirically the next step is to identify the variables that will be investigated. How many variables that can change throughout an experiment should a researcher investigate?

a. Only one variable should change throughout the experiment. b. There are exactly three variables that should change throughout the experiment. c. The number of variables that change can differ based on the particular research question. d. It is impossible to limit the number of variables that can change throughout an experiment.

William James, an important American psychologist, countered the theories of structuralism by introducing his own theory, functionalism, in the United States

Indicate whether this statement is true or false.