In Much of What Is Now Canada,glaciers Covered the Land

In much of what is now Canada,glaciers covered the land as little as 12,000 years ago and glacial erosion scoured the land surface leaving very thin soil or bare rock over large areas.The Midwestern United States was also covered in ice at this time,yet this area contains some of the richest farm land in the world with thick soils.These soils are formed on glacial sediments and windblown dust deposits from the ice age.Why are the soil conditions between these areas so different when the soils are virtually identical in age?

A) It is much colder in Canada so chemical weather is much slower; thus and soils have not had time to form.
B) The Midwestern soils are transported soils with soil development on materials that were already loose,unconsolidated materials.
C) Sea level rose following the ice age and covered the Midwest with an inland sea,rapidly forming soil.
D) The Midwestern U.S.is much flatter than Canada,allowing soils to develop more quickly.