What Accounts for the Disruption of the Agricultural Economy of the Abbasid

What accounts for the disruption of the agricultural economy of the Abbasid empire?

A) The decline of the cities led to a fall in the demand for food supplies and consequent drops in agricultural prices.
B) Progressive desiccation of the region led to a diminution of the land available for agriculture.
C) Spiralling taxation, the destruction of the irrigation works, and pillaging by mercenary armies led to destruction and abandonment of many villages.
D) The government ordered regions of the empire populated by Shi?as abandoned.