Passage Summary: Because we only grow a few types of crops these days, a disease that kills just a couple of those types would be a total disaster for our food supply, unlike in the old days when we grew many more kinds.

Conclusion: A disease affecting only a few crop strains would cause much more damage to the food supply today than it would have several generations ago.

Reasoning: Modern agriculture relies on significantly fewer strains of crops than in the past, resulting in a lack of genetic diversity.

Analysis: The argument assumes that a decrease in the number of strains automatically leads to a higher vulnerability for the entire food supply. To weaken this, we need to find a reason why the current system might not be as fragile as it looks. Look for an answer that suggests modern strains are more robust against disease than older ones, or perhaps that the 'few' strains we use today are so widely distributed that a disease hitting them would have been just as catastrophic in the past. We want to find a fact that suggests the lack of diversity doesn't necessarily lead to the predicted devastation.