When researchers studied whether or not dreaming occurs in non-REM sleep, they found that ________

a. it does, but the dreams are shorter and less vivid than in REM sleep.
b. it does, but the dreams are longer and more fantastical than in REM sleep.
c. it does not, unless the person has been chronically sleep deprived.
d. it does not, unless the person is a patient with a severed corpus callosum.

Answer: a