What is a barrier island?
a. a narrow bank of sand that projects into the water from a bend in the coastline
b. a long ridge of sediment deposited by the longshore current and separated from the mainland
c. a ridge of sand that forms between the mainland and an island connecting the island to the mainland
d. a long ridge of sediment that forms when a spit closes off a bay

answer: option d.

explanation:

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.