If Glaciers Carry a Mixture of Different Clast Sizes,why Are

If glaciers carry a mixture of different clast sizes,why are glacial outwash deposits layered?

A) because clasts fall out of the glacier in size progression
B) because gravity pulls out only the smallest particles
C) because glacial outwash is formed from the bottom of the glacier
D) because the glacier does not deposit the sediments; the river does