Final answer:
The second socialization stage for puppies begins at about 8 to 10 weeks of age, and this is when it is appropriate for them to start living with their new human families.
Step-by-step explanation:
The second socialization stage for puppies typically begins at about 8 to 10 weeks of age. This is the period when it is generally recommended for puppies to leave the breeder and start living with their new human families. During this socialization stage, puppies are highly receptive to learning and forming social relationships, not only with humans but also with other dogs and animals.
It is essential for puppies to have the opportunity to interact with their littermates and mother until at least 8 weeks old. This interaction allows them to develop critical social behaviors and helps prevent issues such as fearfulness or aggression towards other dogs in the future. Puppies that are removed from their litter too early may miss out on important learning experiences and could develop behavioral problems as a result.
Therefore, the correct answer to the student's question is that puppies should start living with their new human family at the beginning of the second socialization stage, which begins at about 8 to 10 weeks of age.