Imbrication is a process that results in:
a. an extremely well-preserved archaeological record that directly reflects human behavior.
b. clay-rich soils pushing artifacts upward as the sediment swells and then moves them down as cracks formduring dry cycles.
c. stones in a riverbed lying with their upstream ends slightly higher than their downstream ends.
d. stones in a riverbed lying with their upstream ends slightly lower than their downstream ends.