Final answer:
The most significant socializing agent on a child's development is Family, which teaches a child what they need to know and how to navigate the world. Family is the first agent of socialization, providing the first experiences of socializing a child to the world.
Step-by-step explanation:
The socializing agent that is thought to have the most significant impact on a child's development is Family. Mothers and fathers, siblings and grandparents, plus members of an extended family, all teach a child what he or she needs to know. For example, they show the child how to use objects, how to relate to others, and how the world works. Family is the first agent of socialization, providing the first experiences of socializing a child to the world.