GRE Reading Comp Challenge: Strengthen the Argument

Verbal | GRE prep | Reading Comprehension | GRE Challenge

GRE Reading Comp Challenge (Pictured: European Robin)

GRE Reading Comp passages usually try to persuade you of something. An argument is given, and your job is to analyze it. Some of the hardest Verbal questions require you to identify information that would strengthen an argument. For practice, try this Reading Comp question that likely just 2 in 10 test takers would get right.

Reading Comprehension: Strengthening Arguments
Difficulty Level: 5 (Very High)

Question Difficulty
  • Very High50
  • High420
  • Medium340
  • Low26080
  • Very Low1100
% of Test Takers Who Answered Correctly

In The Practice Book for the Paper-based GRE, one of the hardest Verbal questions asks you to strengthen an argument given in a short causal reasoning passage. (See §3, 25.) Only 19% of test takers got the question right when it was on a real exam. Here's a question that's similar in structure and difficulty.


This year in the city of Northfield a high number of Robins, small birds that eat earthworms, have been found dead from infectious diseases. Most had high tissue concentrations of certain compounds that, even in low concentrations, reduce Robins' resistance to infection. The only local source of these compounds is the Northfield Chemical Plant. Therefore, since Robins rid their bodies of the compounds rapidly once exposure ceases, their mortality rate should decline rapidly if the chemical plant stops production of the compounds.

Which of the following, if true, most strengthens the argument?

  1. Production of the compounds was lower this year than it was a decade ago at the Northfield Chemical Plant.
  2. In high concentrations, the compounds are toxic to many types of birds.
  3. The compounds break down into harmless substances after a few months of exposure to air, soil, or water.
  4. Earthworms can pass soil contaminants to their predators in low concentrations that cause no harm.
  5. The compounds will not leak into the environment from the Northfield Chemical Plant if the plant improves its waste disposal procedures.

The Explanation

Step 1: Find the conclusion and the premises. When you strengthen an argument, you help defend its conclusion. The conclusion is the claim the argument attempts to support, and the premises are the claims that are supposed to support it.

Sometimes a word like "thus" or "consequently" points you to the conclusion. In the Challenge passage, the last sentence starts with "therefore," a common conclusion indicator.

Therefore, since Robins rid their bodies of the compounds rapidly once exposure ceases, their mortality rate should decline rapidly if the chemical plant stops production of the compounds.

This one sentence makes two claims. The first claim—"Robins rid…exposure ceases"—isn't the conclusion. It's a premise. It begins with the word "since," a common premise indicator. Most important, this first claim has no support in the passage. In other words, the author is just stating an assumption about Robins. Any argument will make some assumptions, but the conclusion will never be one of them.

The second claim—"their mortality…the compounds"—is the argument's conclusion. You're supposed to be convinced that the Robins' death toll will quickly drop once the chemical plant stops making the offending compounds. This prediction is based on observations cited in the passage that are assumed, not argued, to be accurate.

Here's a simple summary of the argument.

  • Premise: This year a lot of Robins in Northfield have died from infectious diseases.
  • Premise: Most of the dead Robins had compounds in them that hurt their  immunity.
  • Premise: The only local source of these compounds is the Northfield Chemical Plant.
  • Premise: Once Robins are no longer exposed to the compounds, Robins quickly remove the compounds from their bodies.
  • Conclusion: If the plant stops making the compounds, then the death rate of Robins in Northfield will quickly fall.

Step 2: Choose the answer that best supports the conclusion. A "strengthen the argument" question will most likely use the pick-one-of-five format that you see in the Challenge problem. Some of the options may not affect the argument's conclusion, others may undermine it, and at least one will support it. Select the answer that, if true, gives the most compelling reason to believe the conclusion.

To start, think about how to cast doubt on the conclusion. The correct answer could help dispel the very objection you raise. Here the conclusion is an "if-then" statement, also known as a conditional statement. To challenge a conditional, explain how the "if" part could be true yet the "then" part still false.

Imagine that the Northfield Chemical Plant stops producing the compounds, yet the local Robins continue to die in droves from infectious diseases, even months after production has halted. Why would that happen? Here are a few potential explanations. Any of these claims, if true, would hurt the argument.

  1. The compounds weren't—and still aren't–reducing the Robins' resistance to infection. OR
  2. The Northfield Chemical Plant isn't the only local source of the compounds. OR
  3. The compounds remain in the Robin's environment indefinitely unless humans conduct a cleanup.

The argument's premises already deny (1) and (2), so an answer choice that contradicted one of those objections wouldn't add anything to the argument. The premises don't address (3), however, so rebutting it would add something. Option (C)—"The compounds break down…"—implies that (3) is false. Thus, (C) helps support the conclusion. In fact, (C) is the correct answer.

The other options either support the conclusion less or not at all. For instance, (B)—"In high concentrations…"—might bolster the link between the compounds and the Robins' reduced immunity by suggesting that those substances correlate with ill-effects in birds. So (B) could reinforce one of the argument's premises. But here's the big difference between (B) and (C). If (B) were false, the argument's conclusion wouldn't really suffer, but it would if (C) were false. The negation of (C)—"the compounds do not break down…"—suggests that the Robin's mortality rate will not decline rapidly if the chemical plant stops making the compounds.

When a Reading Comp question asks you to strengthen an argument, find the conclusion and challenge it. Think of damning objections or contrary evidence. Figuring out how to weaken the argument will help you better understand how to strengthen it.

Want analysis of some more hard problems? Here's a post that covers two official Verbal questions that well over half of all test takers got wrong: Doing GRE Reading Comp Exercises to Prepare for the Argument Essay.

Photo: "Bird - 24.12.2007" by Keven Law from Los Angeles, USA - A very late...or Early Christmas Robin..:O) Licensed under CC BY-SA 3.0 via Commons.