<span>I think the right answer is "which they reach a certain age." Jean Piaget is a psychologist who studied human development. According to his theory, human development is divided into stages, these stages are achieved due to cognitive maturation during the first years of life. <span>Each stage of development is characterized by more specialized skills, behaviors, and cognitive skills.
This would be historical geography because when African slaves were brought to the United States, they were brought to the south to work. Today, many African-Americans still live in the South because that is where their ancestors were brought and lived.
I'd say that the answer is observational study because they're just analyzing the data and if it were an experiment they'd be taking data and comparing it.
