Frequent exposure to low-frequency electrical fields is associated with cancer. Although those fields are far too weak by themselves to...

GMAT Critical Reasoning : (CR) Questions

Source: Mock

Critical Reasoning

Logically Completes

EASY

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Notes

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Frequent exposure to low-frequency electrical fields is associated with cancer. Although those fields are far too weak by themselves to produce the genetic changes that typically promote cancer, they are known to suppress the production of a hormone that prevents overproduction of the hormone estrogen. Excess estrogen is known to promote cancer.

The statements above are structured to lead to the hypothesis that

genetic changes are more likely to promote cancer than is any other single factor

most people are not exposed to electrical fields that are strong enough to produce cancer

exposure to low-frequency electrical fields might cause cancer through hormonal changes

most hormones, when produced in excess amounts, promote cancer

excess estrogen is likely to promote cancer only if it is accompanied by frequent exposure to low-frequency electrical fields

Solution

Passage Analysis:

Text from Passage	Analysis
Frequent exposure to low-frequency electrical fields is associated with cancer.	What it says: Low-frequency electrical fields are linked to cancer What it does: Sets up the main topic and establishes a concerning connection What it is: Study finding/scientific observation
Although those fields are far too weak by themselves to produce the genetic changes that typically promote cancer, they are known to suppress the production of a hormone that prevents overproduction of the hormone estrogen.	What it says: These fields can't directly cause genetic damage but they mess with hormone production that controls estrogen What it does: Explains how the connection works - shifts from "what happens" to "how it happens" What it is: Scientific explanation/mechanism Visualization: Electrical Fields → Block Hormone Production → More Estrogen Gets Made
Excess estrogen is known to promote cancer.	What it says: Too much estrogen leads to cancer What it does: Completes the chain of reasoning by connecting estrogen to the original cancer link What it is: Established medical fact Visualization: Electrical Fields → Less Protective Hormone → Excess Estrogen → Cancer

Argument Flow:

The argument starts with an observed connection, then explains the step-by-step mechanism behind that connection. We move from "electrical fields are linked to cancer" to "here's exactly how that happens through hormone disruption."

Main Conclusion:

The passage doesn't state a direct conclusion but builds toward the hypothesis that low-frequency electrical fields cause cancer through hormone disruption rather than direct genetic damage.

Logical Structure:

This follows a causal chain structure: electrical fields → hormone suppression → excess estrogen → cancer. Each step connects logically to show how something seemingly harmless (weak electrical fields) can still cause serious problems (cancer) through an indirect pathway.

Prethinking:

Question type:

Logically Completes - We need to find what hypothesis the argument is building toward. The passage gives us facts and a mechanism, so we're looking for the logical conclusion that ties everything together.

Precision of Claims

The claims are about specific biological mechanisms: electrical fields suppress hormone production (activity), this leads to excess estrogen production (quantity), and excess estrogen promotes cancer (causal relationship). We need a hypothesis that connects this chain precisely.

Strategy

For Logically Completes questions, we follow the logical flow and see where it leads. The argument establishes: 1) Electrical fields are linked to cancer, 2) They can't cause genetic damage directly, 3) But they suppress hormones that control estrogen, 4) Excess estrogen causes cancer. We need to find what hypothesis this chain of reasoning supports - likely something about HOW electrical fields cause cancer (through the estrogen pathway) rather than direct genetic damage.

Answer Choices Explained

genetic changes are more likely to promote cancer than is any other single factor

This goes completely against what the argument tells us. The passage specifically states that electrical fields are 'far too weak by themselves to produce the genetic changes that typically promote cancer.' The argument is actually suggesting an alternative pathway (hormonal) rather than claiming genetic changes are the most important factor.

most people are not exposed to electrical fields that are strong enough to produce cancer

This misses the point entirely. The argument isn't about how many people are exposed or the strength needed for direct cancer causation. Instead, it's explaining how even weak fields can cause cancer through an indirect hormonal pathway. This choice focuses on exposure levels rather than the mechanism.

exposure to low-frequency electrical fields might cause cancer through hormonal changes

This perfectly captures the hypothesis the argument builds toward. We have the complete causal chain: electrical fields → hormone suppression → excess estrogen → cancer. The word 'might' appropriately reflects the tentative nature of a hypothesis, and 'through hormonal changes' accurately describes the mechanism the passage outlines.

most hormones, when produced in excess amounts, promote cancer

This makes an overly broad claim about hormones in general. The argument only discusses one specific hormone (estrogen) and its cancer-promoting effects when overproduced. We can't generalize from estrogen to 'most hormones' based on this passage.

excess estrogen is likely to promote cancer only if it is accompanied by frequent exposure to low-frequency electrical fields

This reverses the causal relationship. The argument suggests that electrical fields can lead to cancer through estrogen overproduction, not that estrogen needs electrical field exposure to be dangerous. This choice makes electrical fields a necessary condition for estrogen to cause cancer, which isn't supported.

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