I'm guessing its the fall of China's last dynasty or the fall of Qin Shi. Hope I could help
Soviet union
After the Cuban Revaluation of 1959, Cuba became increasingly dependent on the soviet union.
Answer:
Agriculture (and associated population increase) resulted in population seventies and crowding. Accumulation of waste and increased transmission of microbes owing to crowding provided the conditions conducive to the spread and maintenance of infectious disease.
Explanation: