Answer:
C. Serious disease epidemic
Explanation:
A disease outbreak can cause a population crash. This has been well reported in human history. For example, from 1347 to 1351, the number of deaths due to Plague (Pestilence) was up to 200 million in Eurasia. The treatment was not available and a significant population crash was seen.
On the other hand, low death rates, high birth rates, and plentiful resources cannot cause population crash rather they are still reflecting an increase in the population.
