There are approximately functional genes in human chromosomes

Which theory of sleep is based on the premise that sleep evolved to keep humans out of harm's way?

a) restorative b) melatonin c) circadian d) ecobehavioral

The more intelligent a person is the higher grades he or she receives in school. Most likely, this finding comes from which type of research?

a) case study b) epidemiology c) correlational study d) experiment