Why Does the Moon Have a Layer of Powdery "Soil

Why does the Moon have a layer of powdery "soil" on its surface?

A) Large impacts shattered lunar rock to make this soil.
B) The soil exists because the Moon accreted from powdery material after a giant impact blasted Earth.
C) Volatiles escaping from the Moon's interior bubble upward and make the soil.
D) The soil is the result of the same processes that make powdery sand on Earth.
E) It's the result of gradual erosion by micrometeorites striking the Moon.