Question

An ingredient in coffee, known as RTC, has been found to inactivate common cold viruses in experiments. In earlier experiments, researchers found that inactivated common cold viruses can convert healthy cells into cancer cells. It can be concluded that the use of coffee can cause cancer.

Which one of the following, if true, most seriously weakens the argument?

• A. Several teams of scientists performed the various experiments, and all of the teams had similar results.
• B. The carcinogenic effect of RTC could be neutralized by the other ingredients found in coffee.
• C. When RTC kills common cold viruses it weakens the immune system, and this might diminish the body's ability to fight other viruses, including viruses linked to cancers.
• D. If chemists modify the structure of RTC, RTC can be safely incorporated into medications to prevent the common cold.

Hint:

Look for the option that offers a different cause for the cancer risk, one that breaks the argument's assumed "inactivated virus becomes cancerous" chain.

Answer 1

The Correct Option is C

The argument builds a chain: RTC (an ingredient in coffee) inactivates common cold viruses, earlier experiments showed inactivated common cold viruses can turn healthy cells into cancer cells, so coffee use can cause cancer. To weaken this, we need a statement that breaks or casts real doubt on this specific chain of reasoning, not one that just supports it or talks about something unrelated.

1. Option A: several teams got similar results in the experiments. This only makes the original experimental findings more reliable, it does not attack the reasoning that links RTC to cancer. This strengthens the argument rather than weakening it.
2. Option B: other ingredients in coffee neutralize the carcinogenic effect of RTC. This sounds like a weakener, but it does not really challenge whether RTC itself, through the mechanism described, is dangerous. It only asserts a separate, unexplained neutralizing effect, which is a weaker and less direct challenge than option C.
3. Option C: RTC kills the cold virus by weakening the immune system, and it is this weakened immune system, not the "inactivated virus becomes cancerous" mechanism the argument describes, that could let other cancer linked viruses take hold. This gives a completely different explanation for any cancer risk, one that has nothing to do with the specific inactivated-virus-to-cancer-cell pathway the argument relies on. This directly undercuts the argument's own causal chain.
4. Option D: modifying RTC's structure could let chemists use it safely in cold medications. This talks about a future, chemically altered version of RTC, not the RTC naturally present in coffee today, so it does not address whether current coffee use causes cancer.

Option C offers the strongest challenge because it supplies an alternate mechanism for cancer risk (immune weakening opening the door to other viruses) instead of the mechanism the argument depends on (the cold virus itself turning cancer causing after inactivation). This breaks the specific causal link the conclusion needs.

Let's summarize:

• To weaken an argument, attack the causal chain it depends on, not just the general subject.
• An alternate explanation for the same outcome is one of the strongest ways to weaken a "X causes Y" conclusion.

The statement that most seriously weakens the argument is option (C).