Which of the Following Is the Primary Cause of the Collapse

Which of the following is the primary cause of the collapse of the Qin Empire?

A) The Xiongnu invaded the center of the Qin Empire and released the Qin's imprisoned rivals.
B) Qin rule weighted heavily on taxpayers and constant warfare consumed massive tax revenues.
C) Shi Huangdi's son and eldest grandson joined to stage a mutiny against the emperor.
D) Peasants refused to allow their sons to be conscripted into the army, which became too small to keep order.