Final answer:
Increased deaths and increased emigration are the two factors that most likely cause a population to decrease.
Step-by-step explanation:
The two factors most likely to cause a population to decrease are increased deaths and increased emigration. Increased deaths reduce the number of individuals in a population through natural causes such as disease, predation, or accidents. Increased emigration refers to individuals leaving the population to reside in another location. Both of these factors result in a reduction in the overall population size.
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