Normally, the number of cycles of sleep stages that occur per night is ____ cycles.
a. 4 to 6 c. 8 to 10
b. 6 to 8 d. 10 to 12
Question 2
During a typical night of sleep, a normal adult sleeper cycles between non-REM sleep and REM sleep at approximately every ____ minutes.
a. 30 to 60 c. 90 to 120
b. 60 to 90 d. 120 to 150