Passage Summary: Some plants make a special nectar to attract ants that protect them. Scientists noticed jumping spiders also love this nectar, so they think the spiders might be helping protect the plants too.

Conclusion: Jumping spiders likely protect plants that produce extrafloral nectaries from leaf-eating bugs, much like ants do.

Reasoning: Greenhouse experiments show spiders prefer plants with active nectaries and consume the nectar.

Analysis: To strengthen this argument, we need to bridge the gap between the spiders' presence and the plants' protection. Currently, we only know the spiders are attracted to the nectar and eat it, but we don't know if they actually do anything to help the plant in return. Look for an answer choice that shows the spiders actually attacking or deterring the leaf-eating insects. If the spiders are just eating the nectar and ignoring the pests, the author's conclusion would fall apart.