One of the Main Reasons for the Demise of the Tang

One of the main reasons for the demise of the Tang Dynasty was its inability to effectively solve the problem of land distribution. Which of the following statements can serve as a valid explanation for this policy failure?

A) The increasing concentration of land in the hands of the rich and politically influential, coupled with rising food production, led to increasing pressure on the land distribution system.
B) The receipt of large, permanent land grants by government officials fundamentally strengthened the system but undermined the concept of the Mandate of Heaven.
C) Equality in land distribution was successfully maintained through the tax regulations of the central government.
D) Mongol invaders destroyed the Chinese government's bureaucratic infrastructure.
E) Empress Wu confiscated all land, distributing it to illiterate and unprepared peasants.