In Regard to Fetal Activity and Inactivity, Fetuses

In regard to fetal activity and inactivity, fetuses:

A) do not have true sleep states, but they do have periods of inactivity while awake.
B) have periods of high activity and rest while awake, and have both active and quiet sleep states.
C) are essentially asleep most of the day and night, but their sleep can be active or quiet.
D) are in constant motion throughout the day and night.