The correct option is A 12 - 13 years
Sexual maturity or sexual development is the process of physical changes through which a child's body matures into an adult body capable of sexual reproduction to enable fertilization. This is also called puberty.
On average, girls begin puberty or sexual maturity at ages 10-11, boys at ages 11-12.
Thus, the correct answer is option (A), '12-13 years'.