The correct answer is "his primary caregiver can calm him down easily after being separated".
Starting at 6 months of age up to the age of 2 years old, a child may experience what we called separation anxiety. At this age, the child is able to represent in its mind that what he cannot see does not exist. This is manifested by signs of extreme neediness of the child. When the child eventually outgrows this phase, then the child is now securely attached and the caregiver can calm him down easily after being separated.