The study of the endocrine system and genetic mechanisms would most likely be undertaken by a: A. clinical psychologist. B. physiological psychologist. C. social psychologist. D. educational psychologist.

Before answering the question, it's essential to understand the specific roles and areas of work of each type of psychologist mentioned in the question. A. Clinical Psychologist: They diagnose and treat mental, emotional, and behavioral disorders. They typically don't focus on the endocrine system or genetic mechanisms. B. Physiological Psychologist: They study the relationship between the human mind and body, focusing on the biological processes involved in human behavior and cognition. They might research the endocrine system and genetic mechanisms. C. Social Psychologist: They study how human behavior is influenced by social situations and how people interact with others. They generally don't focus on the endocrine system or genetic mechanisms. D. Educational Psychologist: They study how people learn and process information. They develop strategies to improve learning and deal with educational problems. They typically don't focus on the endocrine system or genetic mechanisms.

Based on the roles and focus of each psychologist, it is clear that a physiological psychologist (option B) would most likely undertake the study of the endocrine system and genetic mechanisms, as they research the biological processes involved in human behavior and cognition.

The correct answer is B. physiological psychologist.