The correct answers are:
A. converging plates;
D. a hot spot;
The chains of volcanic islands can be found mostly alongside the borders of the convergent plate boundaries, more specifically, on the convergent boundaries between an oceanic and continental tectonic plates. That can easily be seen by the so called ''Ring of Fire'' where there's numerous chains of volcanic islands.
Also, even though much less in number, chains of volcanic islands can be formed by a hot spot. As the plate moves over the hot spot, the islands that have initially been formed are moving away from the hot spot itself, and new islands are forming over it. This can be witnessed in the case of the Hawaiian Islands.
