Which diffusion type is primarily concerned with the geographical movement of individuals?

Relocation diffusion is the correct choice because it specifically refers to the movement of individuals from one location to another, carrying with them their cultural practices, ideas, and innovations. This type of diffusion ultimately results in the spread of cultural traits as people move and settle in new areas, which can significantly influence the demographics and cultural landscape of the destination location.

The emphasis here is on the movement of individuals themselves, rather than the spreading of ideas or cultural practices through various channels, which is the focus of the other types of diffusion. For instance, stimulus expansion diffusion involves the spread of an underlying principle or idea rather than the direct movement of individuals. Contagious expansion diffusion describes how a cultural phenomenon spreads rapidly and widely, like a viral trend, but does not involve the physical relocation of people. Hierarchical expansion diffusion involves the spread of cultural phenomena from one key individual or node to other individuals or places in a more controlled manner, and again, this description does not center on the direct movement of individuals themselves.