Final answer:
The correct pattern for the average age of menarche onset in Europe from 1840 to present would be a significant decrease, dropping about 4 years due to improvements in nutrition and health standards.
Step-by-step explanation:
If you were asked to describe the pattern of the average age of menarche onset in Europe between 1840 and today, the correct answer would be a. "The average age of onset has dropped about 4 years." Over time, due to improvements in nutrition and health standards, the age at which girls experience menarche has significantly decreased. In the past, the average age of onset of menarche was considerably higher. For example, historical data from the United States shows that the average age of menarche was approximately 17 years in the 1860s. With advancements in nutrition and overall living standards, this average age has declined. Today, the average age of menarche in the U.S. is around 12.75 years, and similar trends can be observed in Europe. Why is this the case? One of the contributing factors to this trend is body fat and the hormone leptin, which is secreted by adipose cells and has a strong role in determining the onset of puberty. In lean and highly active girls, such as gymnasts, puberty onset—including menarche—may be delayed.