PSAT Reading Question 499: Answer and Explanation

Question: 499

The author implies that a property of antibiotics that makes them particularly helpful to diseased animals is that they

• A. are not widely recognized and can therefore be inconspicuous.
• B. cause the diseased tissue to mutate into healthy tissue.
• C. help the organism develop long-term immunity against infection.
• D. attack the bacteria without attacking the host organism.

Correct Answer: D

Explanation:

(D) The answer can be found in the third paragraph, where the author details the mechanism by which antibiotics work. He says that antibiotics target peptidoglycan polymers, which are present only in bacteria. Therefore, antibiotics harm the bacteria without harming the host's cells, choice (D). Choice (A) is incorrect as evidenced by the fact that many bacteria have developed antibiotic resistance. Neither choice (B) nor choice (C) is supported anywhere in the passage.