Answer:
b. Their eyes are likely to move under their closed eyelids.
Explanation:
Vivid dreaming is the term referring to our conscious awareness of a particular state or condition as we dream, resulting in an experience from which we have a very clear and vivid memory, usually appearing to have direct control and ability over our actions, and some sometimes the unfolding of the dream content itself.
Since a vivid dream represents a state of consciousness, it is possible for the person who is having these dreams to move their eyes under closed eyelids.