What causes the subduction zone when an oceanic plate collides with a continental plate?

1) oceanic plates are more dense than continental plates so the oceanic plate dives under the continental plate
2) when the continental plates collide the force is so great that it causes the surrounding crust to collapse
3) continental plates are more dense than oceanic plates so the continental plate dives under the oceanic plate
4) continental plates are more dense than oceanic plates causing the oceanic plate to push upward

This is what I know

Subduction occurs when two plates collide at a convergent boundary, and one plate is driven beneath the other, back into the Earth's interior. Not all convergence leads to subduction. Continental rocks are too buoyant to be forced downward, so when continents collide, they crumple but stay at the surface.

radiative zone

explanation    

radiative zone is the layer of the sun which energy is transferred away from the core by radiation. although, the core is the only part of the sun that produces an appreciable amount of heat through fusion. in fact, 99% of the energy produced by the sun takes place within 24% of the sun's radius.