Final answer:
Menarche is correctly identified by adolescent girls when they define it as a woman's first menstrual period, marking a significant milestone in female reproductive development during puberty.
Step-by-step explanation:
Teaching about menarche was successful when adolescent girls correctly state that menarche is defined as a woman's first menstrual period. Menarche is one of the most significant changes in females during puberty and signifies the beginning of menstruation. This event typically occurs at an average age of 12.5 years in the U.S, but can vary widely due to genetic and environmental factors. Understanding menarche is essential as it marks the start of the menstrual cycle, which includes the cyclic release of an egg and preparation of the uterus for pregnancy, unless the woman is pregnant.