In the Strange Situation,a sign of insecure attachment might be:

A) smiling at the mother when she returns to the room.
B) crying and being unable to be comforted when the mother returns.
C) seeking contact with the mother when reunited.
D) playing happily as long as the mother is present.

Crying and being unable to be comforted when the mother returns is a sign of insecure attachment according to the Strange Situation. This indicates that the child is anxious and uncertain about the mother's availability and whether or not they can rely on her for comfort and support. Option A and D are signs of secure attachment where the child is happy and comfortable in the presence of the mother. Option C could be a sign of either secure or insecure attachment, as seeking contact with the mother when reunited could be a way of seeking comfort or simply seeking interaction.