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Question

Difficulty: MediumStrengthening Arguments

A commercial vineyard introduced autonomous weeding robots designed to eliminate weeds using targeted laser bursts instead of traditional chemical herbicides. After one year of using the robots, the vineyard recorded a 20 percent increase in grape yield per acre compared to the previous year. The vineyard manager concluded that eliminating chemical herbicides in favor of laser weeding directly improved the productivity of the grapevines. Which of the following, if true, most strengthens the vineyard manager's argument?

  1. Neighboring vineyards in the same region that continued using traditional chemical herbicides during the same year experienced no increase in grape yield per acre.Answer
  2. B
    Operating and maintaining the autonomous laser robots required a 15 percent increase in total energy expenditure compared to applying chemical herbicides.
  3. C
    Chemical herbicides traditionally applied in the region are known to wash into local groundwater supplies during severe rainstorms.
  4. D
    The vineyard manager had previously considered switching to manual hand-weeding before choosing the autonomous laser system.
  5. E
    The vineyard experienced unseasonably high rainfall and optimal growing temperatures during the season following the introduction of the robots.

Answer

Neighboring vineyards in the same region that continued using traditional chemical herbicides during the same year experienced no increase in grape yield per acre.
The conclusion asserts a direct cause-and-effect relationship between switching to laser weeding robots and increased grapevine productivity. The statement showing that neighboring vineyards subject to the same climate experienced no yield increase while continuing herbicide use serves as a control group. This rules out broader environmental factors (like ideal weather) as the true cause of the yield increase, thereby significantly strengthening the manager's causal conclusion.

Step-by-Step Solution

1
Identify the premise and conclusion of the argument.
Premise: Grape yield per acre increased by 20% after switching from chemical herbicides to laser weeding robots. Conclusion: Replacing chemical herbicides with laser weeding directly improved grapevine productivity.
Understanding the precise causal link asserted by the author is essential for evaluating candidate strengthening statements.
2
Determine the underlying assumption and potential vulnerabilities.
The argument assumes that no other factor (such as weather, irrigation, or pest changes) was responsible for the increased yield during that year.
Causal conclusions in GMAT Critical Reasoning are vulnerable to alternative causes; ruling out an alternative cause strengthens the conclusion.
3
Evaluate the options to find evidence that eliminates alternative explanations or confirms the causal link.
The statement regarding neighboring vineyards acting as a control group confirms that regional factors (like weather) alone were not responsible for the yield jump, thus isolating laser weeding as the primary driver.
A control group finding directly strengthens a causal claim by ruling out confounding environmental variables.

Key Concept

Strengthening Causal Arguments by Ruling Out Alternative Causes
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Topics

Strengthening Arguments

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