What is a reason that infants who have been sleeping through the night start waking up again between when they are between 18 and 24 months old?

a. They become more aware that they are sleeping by themselves.
b. They have more nightmares.
c. They watch too much television.
d. They drink too many liquids before bedtime.

A. Toddlers develop a more definite sense of themselves and others as they approach age 2, and if they sleep in a bed separate from their parents they become more aware of this separation and more intentional about relieving it by summoning a parent or going into the parents' room.