Final answer:
Divergent boundaries can form island chains through volcanic activity, while convergent boundaries where two continental plates meet are characterized by the formation of mountain ranges and significant seismic activity.
Step-by-step explanation:
Based on the provided description of lithospheric plate boundaries, their activities, and geological characteristics, we can determine the type of boundary and the activity involved. For statement C, if a divergent boundary is forming an island chain, it suggests that the boundary is likely situated over a mantle plume or hotspot which fuels volcanic activity leading to the creation of islands as the oceanic plates move apart.
For statement E, if it's a subduction zone where two continental plates meet, this would imply a convergent boundary. Here, one continental plate would typically be forced beneath the other, forming a mountain range rather than an island chain and potentially causing powerful earthquakes.