Final answer:
David Pelzer mentioned several off-limits topics in his home and his mother's home, including the shape of American houses, the idea of a happy family existence, and the having of personal belongings.
Step-by-step explanation:
In the book A Child Called 'It', David Pelzer mentions that some topics were off-limits in his home and in the home his mother grew up in. The specific topics he named in interviews include the shape and features of American houses, the concept of a happy family existence, and the having of personal belongings such as wallets and rooms for children.