Final answer:
The 20-month-old child is displaying signs of separation anxiety, seeking comfort from their mom when playing with other children their age.
Step-by-step explanation:
Based on the information provided, it seems that the 20-month-old child is displaying signs of separation anxiety. Separation anxiety is a normal part of child development and typically occurs around 8 months to 2 years of age. It is characterized by a child's fear or distress when separated from their caregiver or when in unfamiliar situations.
During this stage, it is common for the child to seek comfort and security from their primary caregiver, which in this case, is the child's mom. This behavior may be observed when the child is playing with other 2-year-old children and repeatedly returning to her mom. It is important to provide reassurance and support to the child during this developmental phase.