Which of the following demonstrates that a child has developed a theory of mind?

Gross motor skills are related to physical development and coordination, not cognitive understanding. While these skills are essential for overall development, they do not indicate a child's ability to comprehend the mental states of others, which is crucial for developing a theory of mind.

While planning for future scenarios reflects cognitive development, it does not specifically demonstrate an understanding of others' thoughts or beliefs. A child may plan responses based on their perspective without recognizing that others may think differently or have different information.

This knowledge reflects an understanding of conservation, a cognitive milestone in child development. However, it pertains to physical properties rather than social cognition or the ability to appreciate differing perspectives, which is essential for theory of mind.

Egocentric behavior indicates a lack of awareness of others' viewpoints, which is contrary to what is required for a developed theory of mind. Such behavior suggests that the child is still centered on their own perspective rather than understanding that others can have differing thoughts and feelings.