Answer:
Location A creates a gap allowing molten material to seep through; Location B melts and recycles the crust.
Explanation:
There are three types of plate types based on the interaction of the plates, convergent, divergent, and transform plate boundaries. The majority of the plate boundaries though fall into one of the first two types. The convergent plate boundaries are the ones where plates collide, with one plate subduction below the other. The divergent plate boundaries are the ones where plates move away from each other and by doing so they open up a gap between them.
At convergent plate boundaries, where the plates move toward each other, one of the plates moves below the other. As it does so, that plate gradually gets into the top part of the asthenosphere and the crust is melting and gets recycled.
At divergent plate boundaries, where the plates move awat from each other, they open up a gap between them that constantly grows. This gap makes it much easier for the magma from the asthenosphere to penetrate to the surface, and so it does, constantly rising to the surface and creating new crust.