Why Is the Regional Metamorphism of Ocean Crust in a Subduction

Multiple Choice

Why is the regional metamorphism of ocean crust in a subduction zone considered separately from regular regional metamorphism?

A) The ocean crust has no hydrous minerals to destroy or recrystallize.
B) Both the basaltic composition and very low geothermal gradient (Low T, Hi P) are unique and lead to different facies than seen in continental rocks.
C) Unlike regular regional metamorphism, this does not occur along plate margins.
D) Because this setting does not involve any strain deformation.