Question

what does the presence of new rock near an oceanic ridge indicate?
there is always a deep - sea trench underneath.
there is evidence of seafloor spreading.
they are made from oceanic crust.
they have iron oriented in different directions.

Explanation:

Seafloor spreading occurs at oceanic ridges. New rock forms as magma rises and solidifies. This process creates new oceanic crust. A deep - sea trench is associated with subduction zones (not directly with new rock at ridges). While new rock at ridges is oceanic crust, the key indication of new rock near an oceanic ridge is related to the process of seafloor spreading. The orientation of iron in rocks (magnetic striping) is a result of seafloor spreading but the presence of new rock itself is more directly evidence of the spreading process.

Answer:

B. There is evidence of seafloor spreading.