This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Oncology, Subject name: Medicine
You are seeing a 62-year-old woman with a family history of breast cancer. She is worried about her future risk of breast cancer, since her mother died of breast cancer at the age of 63. Which of the following features is also a recognized risk factor for breast cancer? 
Select and explain. 
A. early onset of menopause, B. early onset of menarche, C. late-life radiation exposure, D. multiparity
B: early onset of menarche
Answer: B: early onset of menarche 
Explanation: Breast cancer risk is reduced by 20% for each year that menarche is delayed. Early menopause, natural or surgical, also decreases risk. Early (age 18 or 19) full-term pregnancy and multiparity decrease the risk. Radiation exposure is a risk factor primarily in adolescence and is marginal after the age of 40. In summary, there are three important dates in the assessing the risk of breast cancer: age of menarche, age of first full-term pregnancy, and age of menopause.