Which Statement Is True of Sleep Cycles in Normal Sleep

Multiple Choice

Which statement is true of sleep cycles in normal sleep?

A) They last about 90 minutes, have 1 or more stages of NREM sleep followed by REM sleep.
B) They last about 90 minutes and each consists of 1 or more stages of REM sleep.
C) They last about 60 minutes, have 1 stage of NREM sleep followed by REM sleep.
D) They last about 90 minutes and each consist of REM sleep followed by 4 stages of NREM sleep.