Final answer:
Sentence B) explicitly connects the strain on resources to the increasing population, revealing a causative relationship.
Step-by-step explanation:
The sentence that helps the reader understand that a rise in population might have been a factor in the crisis is B) "Experts believe that the strain on resources was exacerbated by the growing number of inhabitants." This sentence directly links the strain on resources to the increase in population. It makes clear that the experts' belief is that the population growth has made the resource scarcity worse, indicating a causative relationship between the rising population and the crisis.