Answer:
B. Peer
Explanation:
When looking at studies relating to the heredity of traits we want to see if the child got a trait from the parents and their genes or from the way the child grew up with the parents. That means that peers are not useful to us in those studies. Family is very useful since we need to look at the family and how it raises a child. Adoption is useful to see if an adopted child has the same traits as a biological child. And twins are useful if they grew up in different circumstances from one another.
