Passage Summary: Lydia argues that squirrels want the sugar in tree sap. She figures it's either the water or the sugar they're after, and since they can get water easily from other places, sugar is the only logical choice left.

Conclusion: Squirrels are likely drilling into maple trees to obtain sugar rather than water.

Reasoning: Since sap consists almost entirely of water and sugar, and water is easily found elsewhere, the squirrels must be targeting the sugar.

Analysis: Lydia’s argument is a classic example of the 'disjunctive syllogism' or the process of elimination. She identifies two—and only two—possible motivations for the squirrels' behavior. By providing evidence to rule out the first possibility (water), she concludes that the second possibility (sugar) must be the correct one. When identifying her method of reasoning, focus on this structural move of narrowing down options to arrive at a single explanation.