A formal region is A. derived from people's sense of identity and attachment to different areas.
B. an area that possesses one or more unifying cultural or physical traits.
C. an area unified by a specific social, cultural, or economic activity.
D. nonexistent in developing nation.​

a mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. this uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.a geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged.