Earthquakes and volcanoes occur mostly in _______________.
Earthquakes and volcanoes happen frequently in the folded and faulted region. An earthquake is a series of seismic waves or trembles in the earth's crust. They usually happen along the edge of plate boundaries in areas termed as fault lines. They are instigated when pressure builds up at the edge of the plates as they collide or slide past one another.
So the above information shows that Earthquakes and volcanoes occur mostly in Folded and faulted region. Thus correct option is D. Other options are not suitable.