Do strong electric currents, by means of the electromagnetic fields that accompany them, cause cancer in people who live and work nearby? Telephone line workers, who work near such currents every day, can provide a test case. They show elevated levels of brain cancer, therefore, the hypothesis of electromagnetic causation is supported. Which of the following if true, most seriously weakens the argument?
Show Hint
- Burying power lines and other measures to protect the public from such electromagnetic fields would be prohibitively expensive.
- Telephone line workers are exposed to levels of chemical solvents high enough to cause brain cancer.
- High exposure to strong electromagnetic fields is correlated with a slightly higher-than-normal incidence of childhood leukemia, which is a form of cancer.
- Public health officials who found that a group of different illnesses in people living near a power substation could not reliably be attributed to its electromagnetic field were accused of covering up the facts.
- Telephone line workers, like most people, have electrical appliances at home, and most electrical appliances, when turned on, are surrounded by and electromagnetic field of some measurable level.
The Correct Option is B
Solution and Explanation
This question asks us to weaken a causal argument. The argument concludes that electromagnetic fields from strong currents cause brain cancer. The evidence is that telephone line workers are exposed to these fields and have elevated rates of brain cancer. A strong weakener will provide an alternative cause for the observed effect.
Step 2: Detailed Explanation:
Let's break down the argument:
- Observation 1: Telephone workers are near strong electric currents (and their electromagnetic fields).
- Observation 2: Telephone workers have elevated levels of brain cancer.
- Conclusion: The electromagnetic fields (from Observation 1) caused the brain cancer (from Observation 2).
To weaken this, we need to find another possible cause for the brain cancer in this specific group of workers.
- (A) The cost of prevention is irrelevant to whether the fields cause cancer.
- (B) This provides a clear and plausible alternative cause. It states that these same workers are exposed to another known carcinogen (chemical solvents) that is capable of causing the specific effect (brain cancer). This suggests the cancer may be caused by the solvents, not the electromagnetic fields, thus weakening the original conclusion.
- (C) This statement actually strengthens the original argument by showing another correlation between electromagnetic fields and a different type of cancer.
- (D) The actions or accusations against public health officials in a different case are irrelevant to the argument about telephone workers.
- (E) This suggests that the workers' exposure is not unique, which might slightly weaken the idea that they are a special "test case," but it doesn't provide a strong alternative cause for their elevated cancer rates compared to the general population. Option (B) provides a much more direct and powerful alternative explanation.
Step 3: Final Answer:
Option (B) most seriously weakens the argument by introducing a confounding variable—exposure to chemical solvents—that could be the actual cause of the brain cancer.
Top Questions on Logical Reasoning
Disregard commonly known facts. Which conclusion would follow on the basis of given statements only?
Statement (I): Some bottles are car. Some cars are cycle.
Conclusion: \[\begin{array}{rl} \bullet & \text{[(I)] Some bottles are cycle is a possibility.} \\ \bullet & \text{[(II)] All bottles are cycle.} \\ \end{array}\]
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Statement (II): C is shorter than A and A is shorter than E.- CUET (PG) - 2025
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Statement (I): Only three boxes are kept above D and only one box is kept between D and Q. Q is kept lower than D and is immediately below P.
Statement (II): Only one box is kept between A and C. C is kept three boxes above Q. As many boxes are kept above B as are kept below R.- CUET (PG) - 2025
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