Your mother points out to you a magazine article that says better nutrition is the reason modern Americans are taller than Americans of two centuries ago. What is a valid statement that would contradict this?

This is  true, because the advent of genetic engineering and different nutritional researches  have greatly enhanced  the Nutritional values in foods, with resultant increases in the growth and development of cells and tissues from increase growth hormones metabolism. However, reduction in the outbreak of disease, due to advancement in medical research and drug manufacturing are another factors which may contribute to this

Explanation:

c.more precipitation,but only when emission levels.