Final answer:
A researcher focused on the inheritance of behavioral traits such as height and weight is most likely influenced by Charles Darwin, as his theories align with the genetic underpinnings and evolutionary psychology perspective of such research. Thus, the option a is the correct answer.
Step-by-step explanation:
A researcher interested in the inheritance of behavioral traits such as height and weight is most likely influenced by Charles Darwin. Darwin's theory of evolution emphasizes the role of genetic inheritance and natural selection in the development of behavioral traits. This approach aligns with the field of evolutionary psychology, which investigates how certain behaviors may have been advantageous for survival and therefore passed down through generations. Researchers, including those in behavioral genetics, also study the interplay of genes and the environment in shaping individual behavior. The method often used in such research includes twin and adoption studies to parse out genetic and environmental factors. The influence of Darwin in this field is more pronounced as it relates to genetically driven behaviors that have evolved over time rather than focusing solely on learning or environmental factors as suggested by behaviorists like B.F. Skinner.