Mount StHelens and the Other Cascade Volcanoes Are ________

Mount St.Helens and the other Cascade volcanoes are ________.

A) young,active stratovolcanoes built on a continental margin above a sinking slab of oceanic lithosphere
B) a row of young,active,shield volcanoes built as western North America moved over a hot spot deep in the mantle
C) old,deeply eroded stratovolcanoes built before the Pacific Ocean existed
D) old,deeply eroded,basaltic shield volcanoes built when western North America was over the present-day site of the Hawaiian hot spot