Answer:
D. It's common in many babies.
Step-by-step explanation:
Separation anxiety is a disorder in which a person experiences excessive anxiety when being separated from home or from people with whom he has a strong attachment. A lot of babies experience this, particularly between six or seven months old until about three years old. Because of this, it is not considered atypical. However, it can be a problem when these feelings continue during adolescence and adulthood.