The great plains region was formed due to which of the following?
a. tectonic activity
b. the creation of primary landforms
c. the weathering of surface material
d. deposition of sediment by water, wind, or ice
*multiple select question*

Afarmer who is grown corn for the past five years notices in the sixth year that the his harvest is significantly smaller, despite an increase in labor on the farm. the following year, the harvest continue to decline. which of the following explanations most plausibly accounts for the reduction in corn yield? a) soil degradation b) desalinization c) better irrigationd) terracing