You would expect volcanoes that are sometimes
explosive and with andesitic magma/ lava with silica content of about 60% .

a) rift zones
b) oceanic hotspots
c) subduction boundaries
d) continental hot spots

c) subduction boundaries

Explanation:

The subduction boundaries, also known as convergent boundaries, are the ones that most commonly give rise to intermediate (andesitic) volcanoes. These volcanoes are know by the term strato volcanoes. The magma from these volcanoes has a relatively high silica content, making it highly viscous. That also means that the magma manages to trap the gasses in it, thus increasing the gas content in it. This results in very explosive and effusive eruptions, because as the magma moves toward the surface, the pressure and temperature significantly change, causing the trapped gasses to explode. This type of magma comes as lava flow, but because it is highly viscous, it only manages to come out on a very small area around its source.

answer is  

loa ≅ lma

to prove that the triangles are congruent using the aas congruence