What is slab pull?

options:

the edges become denser and gravity acts on these raised edges, pulling them downward and away from one another

currents just beneath earth's crust flow very slowly, causing movement in the plates above them

cooler, denser crust sinks into the mantle

folding and crumpling and sliding upward creating mountains

The answer is cooler, denser crust sinks into the mantle.

Explanation:

We live on Earth's crust, its thinnest and outermost layer. This layer is made from many smaller pieces called tectonic plates. These plates are not immobile; they are constantly moving to get closer to or further from each other. One of the main driving forces for tectonic plates movement is slab pull. Not all plates have the same density or temperature; oceanic plates are usually denser and colder the continental ones. Slab pull occurs when these two plates come completely next to each other and the denser oceanic plate subducts the continental, which means that it starts sinking below it, towards the asthenosphere (upper mantle), so the correct answer is cooler, denser crust sinks into the mantle.

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

explanation: