The best answers are:
A) Frontier Warfare
B) Ongoing Corruption
D) Excessive Taxation
The Chinese resented Mongol rule, who oversaw the Yuan Dynasty, and largely felt that they had lost the Mandate of Heaven by the late 1300s. This was largely due to national disasters and plague, and was compounded by the rulers having few resources to deal with them due to constant warfare, corruption, and resulting high taxation.
