The correct answer is A. She provides statistics to show how harmful a poor diet can be.
Step-by-step explanation:
In this section of the article, the author focuses on explaining the negative effects of unhealthy diets, which shows the author believes eating a healthy diet is essential and the opposite has harmful consequences. Additionally, the author develops this idea by using statistics or numerical data. This can be seen in "More than one out of three adults in the United States -- 37.5 percent -- are obese" or in "childhood obesity has tripled in the last 30 years" because the author uses numerical information to point out the negative consequences of unhealthy diets. Thus, the way the author develops her argument is by providing statistics to show the negative effects of a poor diet.