Final answer:
The Socio-Ecological Model is the most suitable to describe the internal and external factors that contribute to disparity, as it addresses individual, relationship, community, and societal factors.
Step-by-step explanation:
To describe the internal and external factors that contribute to disparity, the most fitting model is The Socio-Ecological Model. This model considers the complex interplay of individual, relationship, community, and societal factors. It recognizes that behaviors are influenced by several environmental dimensions and that changes at multiple levels are often necessary for sustainability.
The Health Belief Model could also be applicable as it relates to individual perceptions and actions regarding health behaviors, but it does not address external factors as comprehensively as the Socio-Ecological Model does.
The Diffusion of Innovation Model focuses on the adoption of behaviors or technologies over time within a society, which may indirectly relate to disparities. Meanwhile, The Ecology of Human Performance Model looks at the transactional relationship between individuals and their environments, which can also offer insight into disparities, though not as specifically as the Socio-Ecological Model.