Passage Summary: Mark thinks two drugs that work the same way will have the same bad side effects, but Kathy argues that because they are made of different chemicals, they probably won't.

Conclusion: The drug Qualzan likely does not share the same heart attack side effects as the drug Zokaz.

Reasoning: While both drugs function through the same physiological mechanism for decongestion, they are chemically distinct, which suggests their side effects will differ.

Analysis: Kathy's strategy is to undermine Mark's analogy. Mark assumes that because the drugs are similar in one way (mechanism), they must be similar in another (side effects). Kathy counters this by introducing a relevant difference (chemical composition) that breaks the link Mark is trying to establish. Look for an answer that describes this technique of pointing out a significant difference to challenge a conclusion based on a similarity.