Which developmental milestone must be reached before an infant experiences separation anxiety? (a) imprinting (b) theory of mind (c) conservation (d) egocentrism (e) object permanence?

Object permanence is the developmental milestone that must be reached before an infant experiences separation anxiety.  It is used to describe the ability of a child to know that objects continue to exist despite the fact that they can no longer be perceived that is , seen or heard, touched, smelled, or sensed in any way. This milestone is developed through touching and handling objects by the infants.

The answer is telescope.