Question

Read the passage and answer the following question.
Epidemiologists concerned with the spread of the hantavirus from rats to humans conducted an experiment to explore the effectiveness of a particular pesticide. They exposed a population of 100 rats to the pesticide on day 1. After exposure, they allowed any rats that survived to reproduce. They monitored the population of rats for 100 days and plotted a graph of the data they collected.
The results of this experiment is explained by

• A. Some rats developed a resistance to the pesticide.
• B. Some rats were resistant to the pesticide at the outset of the experiment.
• C. No rats were resistant to the pesticide.
• D. The rats evolved a resistance because they needed to

Answer 1

The correct option is B Some rats were resistant to the pesticide at the outset of the experiment.

Some rats apparently were resistant to the pesticide. They had the selective advantage after exposure to the pesticide, those who were susceptible to the pesticide died. The only rats that survived to pass their genes for resistance to their offspring were the ones that were resistant.

Therefore, the correct answer is option B.