One main reason for the fall of the Mongol Empire was

Athe spread of diseases brought by Europeans.
Bmilitary invasions by Muslim armies.
Ca weakened economy due to expensive public works projects.
Ddecreased trade with the West after the closing of the Silk Road.

Verified Answer :

I think the. answer is B

Answer:   A weakened economy due to expensive public works projects.

Explanation:  Large amounts of money spent on public works projects greatly weakened the economy. This, along with the growing discontentment among the Chinese people, led to the fall of the Mongol Empire.