The formation of new layer of floor in the ocean is called seafloor spreading. It is a geological process which is caused due to the volcanic activity.
In this the new oceanic crust is formed due to the volcanic activity and the older rocks move away from the mid oceanic ridge.
The new layer formed lies in the middle of the ocean and the older rocks or floor moves aside.
This process occurs due to the divergent plates and the gap between them increases forming new oceanic ridge.
I think the correct answer from the choices listed above is option A. It is the alveoli that is composed of single layer <span>surrounded by a network of capillaries. These are used to allow oxygen and carbon dioxide to move from the lungs to the bloodstream.</span>
