Passage Summary: Researchers noticed that people with cancer couldn't process a specific sugar in yogurt as well as healthy people could, so they decided the sugar itself must be causing the cancer.

Conclusion: Consuming galactose in amounts that exceed the body's processing capacity is a cause of cancer.

Reasoning: A study showed that cancer patients and healthy people ate the same amount of yogurt, but the cancer patients had lower levels of the enzyme needed to break down the galactose found in that yogurt.

Analysis: The argument suffers from a classic 'correlation vs. causation' error. It observes that cancer is associated with high levels of unprocessed galactose and immediately blames the galactose. To weaken this, look for an answer that suggests the causal arrow points the other way: perhaps the cancer itself (or the treatment for it) depletes the enzymes needed to process galactose. Alternatively, a third factor could be causing both the cancer and the enzyme deficiency, which would mean the galactose is just an innocent bystander.