Passage Summary: Nicotine is bad for the heart, but people who smoke it get sick more often than people who chew it, even when they take in the exact same amount of nicotine.

Reasoning: Nicotine is known to cause heart problems, yet cigarette smokers have higher rates of these issues than tobacco chewers who ingest the same amount of nicotine.

Analysis: The core of this puzzle is that nicotine alone doesn't explain the difference in health outcomes between these two groups. Since the nicotine levels are equal, we need to look for something else in the smoking process—perhaps the smoke itself or other chemicals—that makes it more dangerous than chewing. We are looking for the answer choice that fails to explain this gap, meaning it either addresses something irrelevant or actually makes the discrepancy harder to understand.