The aleutian islands extend westward from southern alaska to form the northern boundary of the pacific ocean. these volcanic islands were formed by the a. subduction of a continental plate (b. subduction of an oceanic plate)-answer but why is this the answer? c. divergence of a continental plate d. divergence of an oceanic plate

The correct answer is B

Subduction of a ocean plate.

Aleutian islands extend westward from southern Alaska to form the northern boundary of the Pacific Ocean when the Pacific plate gets subducted under North American Plate at a dip of 45 degrees. The pacific  is an oceanic tectonic plate that lies beneath the Pacific Ocean. And thus the correct answer is option B