Mount St Helens and the Other Cascade Volcanoes from Mt

Mount St. Helens and the other Cascade volcanoes from Mt. Shasta in northern California to Mt. Garibaldi in southwestern B.C. are__________ .

A) a row of young, active, shield volcanoes built as western North America moved over a hot spot deep in the mantle
B) young, active composite cones built on a continental margin above a sinking slab of oceanic lithosphere
C) old, deeply eroded composite cones 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