In girls, development of breast and on-set of menstrual flow are sign of

Growth refers to physical changes and development in the body. Breast development and menstruation are signs of physical growth during puberty.

These changes indicate the body is growing and maturing. While they happen during adolescence, they are specifically signs of physical growth and development.

Growth is the most accurate answer because it directly describes physical body changes. These developments show the body is growing from child to mature form.