The Fitbit Smartwatch Determines the Quality of Sleep Related to the Major

The Fitbit smartwatch determines the quality of sleep related to the major categories of sleep. Which of these are used to determine the quality of sleep, also known as the sleep score?

A) the amount of time slept
B) the amount of time spent in deep sleep
C) the amount of movement during sleep
D) All three of these are used to determine the sleep score.