Fact 1: Having no natural predators increases population size.

Fact 2: Population size is a function of natality and mortality.

Given the two facts above, answer the question "having what is a cause of mortality" with the following options: 
- natural predators
 - seasons
 - Abnormal cell growth
 - liver cancer
 - insects
 - chickenpox
 - influenza
 - sunlight


 

 natural predators        