PSAT Reading Question 99: Answer and Explanation

Question: 99

In lines 84–90 ("To avoid…surfactants"), what is the most likely reason the author of Passage 2 compares detergents and bacterium?

• A. To justify research into surfactants from bacterium, since the surfactants in soap may cause some issues in industrial use
• B. To alert companies that want surfactants for paint and varnish to the dangers of bacterium
• C. To show that soap can help reduce the movement of particles to the edge of a stain, but can't stop it
• D. To contend that soap is a better surfactant so it's best to avoid using Pseudomonas aeruginosa until further studies have been done

Correct Answer: A

Explanation:

A

The question asks why the author of Passage 2 compares detergents and bacterium. Although this question asks about a specific line reference, it asks about it in relation to the author's purpose in the passage as a whole. Because this is a general question, it should be done after all the specific questions about Passage 2. Lines 70–74 state, In various industrial applications…the coffee ring effect can be particularly troublesome and scientists have long been seeking ways to counteract it. Then the passage states that researchers have described a solution based on…a particularly promising bacterium, Pseudomonas aeruginosa. Lines 82–91 say that Pseudomonas aeruginosa…produces substances that counteract the coffee ring effect. These surface-tension-disrupting substances are called surfactants. Detergents such as soap are also surfactants. Therefore, the author compares the bacterium and soap as surfactants that may help solve the coffee-ring problem in industrial applications. Look for an answer choice that matches this prediction. Choice (A) mentions research into surfactants and issues in industrial use, so keep it. Eliminate (B) because the passage doesn't address the dangers of using the bacterium in industrial applications such as paint and varnish; it says it is dangerous in open wounds. Choice (C) is a Deceptive Language trap answer; the passage does mention that soap can help reduce the movement of particles to the edge of a stain, but this doesn't explain why the author of Passage 2 compares detergents and bacterium. Eliminate (C). The passage does not state that soap is a better surfactant, so eliminate (D). The correct answer is (A).