In a convection cycle, what causes plastic-like material to sink? a. it loses heat to the crust. b. it gains heat from the crust. c. it loses heat to the outer core. d. it gains heat from the outer core.

How do hearths affect cultural diffusion? a. a hearth is the destination of cultural diffusion. b. a hearth divides a cultural region in two. c. a hearth is the beginning point of cultural diffusion. d. a hearth is the means of cultural diffusion. e. a hearth is the meeting point of two diffuse cultures.