Earthquakes are distributed mainly at the margins of tectonic plates. Which option best describes this?

• A. They occur only at mid-ocean ridges
• B. They occur mainly at the margins of tectonic plates
• C. They occur only on continents
• D. They occur in the upper atmosphere

Answer: (B)

Earthquakes happen where rocks are stressed by the movement of tectonic plates and then rupture to release energy. The strongest and most frequent seismic events occur along plate boundaries, where plates interact by sliding past each other, pulling apart, or colliding. This makes “they occur mainly at the margins of tectonic plates” the best description, since it captures the global pattern of earthquakes being concentrated at these boundaries—including mid-ocean ridges, subduction zones, and transform faults, as well as earthquakes on continental crust.

The other ideas don’t fit because earthquakes are not limited to mid-ocean ridges alone, nor are they restricted to continents only. And they do not happen in the upper atmosphere.