Final answer:
The convergent boundary, or subduction boundary, is most likely to have hot flow due to the subduction of oceanic crust, which leads to regions of high pressure and temperature, melting the crust into magma. Option D is correct.
Step-by-step explanation:
The tectonic boundary most likely to have hot flow is the convergent boundary (Option D: Subduction boundary). This is because, at convergent boundaries, oceanic crust is often forced beneath another plate into the subduction zone, where it moves into regions of high pressure and temperature, eventually melting below the surface. This process creates magma, which can lead to volcanism.
Additionally, the hydration of minerals in the subducting oceanic crust can lower the melting temperature of the mantle above the subducting plate, further facilitating the production of magma. This process is known as flux melting. The deep earthquakes and the pattern of increasing earthquake depth from the coast to inland at subduction zones demonstrate the presence of these active subduction processes.