The correct option is A Puberty
The process of physical changes through which a child's body matures into an adult capable of sexual reproduction to enable fertilization is called puberty. It is initiated by hormonal signals from the brain to the gonads or reproductive organs: the ovaries in females and testes in males.
Menstruation is woman's monthly shedding of the endometrium layer, upon not fertilising the released ovum.
Gestation is the process of carrying of an embryo in the womb of viviparous animal between conception and giving birth.
Fertilization is the process of fusion of male and female gametes.
Thus, the correct answer is option A.