Final answer:
Stranger anxiety is shown when an infant is upset by being held by someone unknown, a sign of cognitive and emotional development related to attachment.
Step-by-step explanation:
The situation that demonstrates stranger anxiety is when an infant around 7 months old feels uncertain and upset about being held by someone unfamiliar to them. This response is typically observed as part of their cognitive and emotional development and is closely associated with the concept of attachment. Based on Mary Ainsworth's Strange Situation procedure, different attachment styles can be observed, ranging from secure to disorganized attachments, but it is the child's response to unfamiliar individuals that characterizes stranger anxiety.