Final answer:
The mean age at which girls begin their growth spurt during puberty is around 9 to 11 years old, with the correct answer being approximately 12 years.
Step-by-step explanation:
The mean age at the beginning of the growth spurt in girls is typically around 9 to 11 years of age, with peaks in growth occurring at about age 11.5. During this period, known as the adolescent growth spurt (AGS), girls can grow approximately 3 inches per year. The pubertal growth spurt for girls is characterized by the development of breast tissue and pubic hair, followed by an increase in height, and ultimately, the commencement of menstruation.
The correct answer to the question is therefore Option C) 12, considering that some girls may start slightly earlier but the average is around this age. It is important to note that individual development can vary widely.