Question

An island arc complex is formed where

Answer 1

An island arc is a type of archipelago (island group) in an arc shape, often made up of volcanoes. They are found close to converging (or destructive) plate boundaries where an oceanic plate subducts another. An example is the Philippines and the Antilles.

Answer 2

Two  oceanic plates converge.

The term 'island arc' is a little subjective. Volcanic arcs in general form above subduction zones either at ocean-ocean or ocean-continent convergent boundaries. Some geologists would restrict the term island arc to ocean-ocean boundaries, but in reality there is a continuum between oceanic volcanic arcs and continental volcanic arcs.