Okay so I'm not sure exactly if this is talking about primary or secondary sources, but if it is then I'm fairly certain that this would be a secondary source since the student wasn't there to witness it, they're relying on their research to give them information.
<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.
I hope my answer can help you.
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When the earths tech tonic plates moved the pushed the land up to form the alps
