Besides the mantle plume below which is the cause of some of the ongoing volcanic activity, Iceland has grown to the size it is because it also
a. has volcanic activity from being on top of an oceanic-oceanic subduction zone
b. has volcanic activity from being on top of a mid-ocean ridge
c. has volcanic activity from being on top of an oceanic-continental subduction zone
d. has volcanic activity from being on top of a large transform fault
