Reading Comprehension Student Worksheet featuring a diagram of ocean floor geology.

1. The feature at A is a mid-ocean ridge. It is an underwater mountain range formed by plate tectonics, where new oceanic crust is created as magma rises from the mantle and solidifies.
2. The process at B is subduction. This occurs when one tectonic plate moves under another, typically an oceanic plate beneath a continental plate or another oceanic plate. The result is the recycling of old oceanic crust back into the mantle, which can cause earthquakes and volcanic activity.
3. As new molten material rises from the mantle at mid-ocean ridges, it pushes the older oceanic crust away. This causes the older crust to move laterally across the ocean floor until it eventually reaches a subduction zone, where it is forced down into the mantle and recycled.