what was the most significant cause of the llkhanates collapse?

a ) the llkhanate collapse because the ruler did not have a male heir.
b ) the llkhanate collapsed because of the support its sufism.
c ) the llkhanate collapsed because of internal revolts by the han chinese.
d ) the llkhanate collapsed because it was devastated by the bubonic plague.

d) the Ilkhanate collapsed because it was devastated by the bubonic plague.