New crust typically forms from separating plates, so it would be A: divergent boundary.
Explanation:
The Earth is comprised of many plates that float on the hot magma in the mantle layer. They are constantly moving but its so slow we can't feel it. A long time ago, all the land on Earth was connected in one big continent named Pangaea. As the plates have moved the land has separated forming the continents.
When plates come together they cause friction between them. This causes the plates to push up forming a mountain. This was how the Himalayan mountains were formed.
Earth was able to retain an atmosphere because of its gravity. It is <span>the same force that keeps us anchored to Earth. Molecules in our atmosphere are constantly moving, spurred on by energizing sunlight. If Earth were much less massive, gravity's grip would be weaker.</span>