Hello!
As you know, the Ring of Fire is a string of active and dormant volanic sites and seismic activity stretching from the Americas to Asia and down to Australia in the Pacific Ocean. This area has around 450 volcanoes (if not more) and is full of many trenches, which are deep and narrow excavations.
In this case the most likely cause of volanic activity in the area is best said to be b. The movemenet of mantle rock through the cracks between tectonic plates
These movements are also the same reason that explains the earthquakes that primarily occur in this region.
Hope this helps and if you need anymore clarifaction feel free to ask.
