The Slight Eastward Slope of the Great Plains Was Created

The slight eastward slope of the Great Plains was created during the Cenozoic by ________.

A) uplift of the western U.S.due to the formation of the Rocky Mountains
B) uplift of the western U.S.due to volcanic activity
C) deposition of sediments shed from the eroding Rocky Mountains
D) uplift of the expanding Basin and Range Province
E) tilting of the U.S.because of sediment deposited on the trailing edge of the plate