Physical activity is most likely to protect women against breast cancer if​

A) ​they begin a physical activity program when young and maintain physical activity.
B) ​they postpone physical activity until after menopause.
C) ​they begin a physical activity program when young and then stop or greatly reduce exercise after menopause.
D) ​they are married and have at least one child.

Starting a physical activity program when young and maintaining physical activity has been shown to have the greatest protective effect against breast cancer. Postponing physical activity until after menopause or reducing exercise after menopause may still have some protective effect, but it is not as strong as consistent exercise throughout a woman's lifetime. Being married and having at least one child does not have a significant impact on breast cancer risk reduction through physical activity.