Ampicillin and other modern antibiotics kill a much wider variety of bacteria than penicillin does. They also carry h...

Irina on September 9, 2019

@Ame15,

The stimulus tells us that modern antibiotics kill a much wider variety of bacteria than penicillin and concludes that using new antibiotics where they might otherwise be unnecessary is likely to result in an outbreak of diseases caused by drug-resistant bacteria.

The correct answer choice (A) bridges the gap between the premise and conclusion saying that drug-resistant bacteria flourish in the absence of competition from a wide variety of other bacteria, resulting in the following chain:

use modern antibiotics -> wider variety of bacteria is killed -> drug-resistant bacteria flourish-> outbreak of diseases caused by drug-resistant bacteria.

(D) tells us that the treatment with new antibiotics is more expensive. This fact fails to demonstrate why treatment with new antibiotics would result in an outbreak of drug-resistant bacteria-related diseases, though it could be an attractive answer choice if the conclusion merely said that new antibiotics are likely to result in more diseases overall, then we could perhaps infer that the high cost of treatment prevents doctors from using them, resulting in disease outbreaks overall. But since the conclusion specifically focuses on drug-resistant diseases, the correct answer choice must provide the link between modern antibiotics and drug-resistance.

Let me know if this helps and if you have any further questions.

Ame15 on September 10, 2019

Thank you! This is very helpful!