Passage Summary: Global warming is making a weather pattern called El Niño happen more often, which makes it rain a lot in one specific area. Since rain usually means more rats and mice, that area is about to get a lot more of them.

Conclusion: Rodent populations in region T will likely increase in the coming decades.

Reasoning: Global warming will make El Niño more frequent, El Niño brings heavy rain to region T, and heavy rain typically leads to more rodents.

Analysis: The ecologist is predicting a rodent boom based on a chain of events: global warming leads to El Niño, which leads to rain, which leads to rodents. To weaken this, you should look for a break in that chain, particularly between the rain and the rodent population. Perhaps the 'heavy winter rainfall' mentioned is actually harmful to rodents, or maybe other environmental factors in region T will counteract the population growth. Focus on finding an answer that suggests the 'sustained rain' rule doesn't apply here.