Why Would the Gravity Anomaly Over a Deep-Ocean Trench Be

Multiple Choice

Why would the gravity anomaly over a deep-ocean trench be negative?

A) because the bathymetry of the trench dips very far below sea level
B) because the crust being pulled into the trench is less dense than sediments above
C) because water fills the space above the subducting slab and is much less dense than rock
D) because the buoyant magma created at the subduction zones is less dense than the rock