The correct answer is B) extremely variable across geographic regions and ethnic groups.
According to the text, rates of physical growth during middle childhood are extremely variable across geographic regions and ethnic groups.
This is true because physical growth during middle childhood can vary depending on different factors such as genes, nutrition, exercise habits, or the environment. A child that is used to physical activity, practice a sport, learn different abilities, has good nutrition, and sleeps correctly, would be more healthy than other children that are more passive or live a more sedentary life. And if we add the issue of genes, we understand that the information can be extremely variable across geographic regions and ethnic groups.
