Why Can Dune Sand,which Can Easily Spread on a Beach,be

Why can dune sand,which can easily spread on a beach,be easily eroded during a storm?

A) Dune sand is finer grained and thus more easily moved by waves.
B) Dunes are at the upper limit of the waves where the waves can easily drag them back downslope.
C) Dune sand stands at a steeper slope than the beach, so it can easily move down to the beach.
D) Dune sand is rounder grain than beach sand, so it easily rolls down the beach.
E) Dune sand is more angular than beach sand, so the grains do not fit together well.