How many chromosomes are found in a normal human cell?

Epidemiology is the scientific study of the

A. effects of diets. B. biological treatment of diseases. C. frequency and distribution of disorders. D. classification systems for mental disorders.

Dr. Barant is studying reaction times and plans to define reaction time in terms of the time it takes to press a button on a display panel. Defining reaction time in this way would:

a. be a testable hypothesis b. provide empirical verification of the concept c. represent an operational definition d. violate general research ethics