This Wind-Blown Dust Deposit (Loess)in Illinois

This wind-blown dust deposit (loess) in Illinois:

A) was deposited by a huge flood of seawater that covered the land at the time of the dinosaurs
B) began as clay and silt that were produced by grinding of rocks along ice-age glaciers
C) forms a world-wide layer associated with a well-known extinction of dinosaurs
D) all of these