Answer: Internal fertilization
Explanation:
Internal fertilization is a process in which the fertilization of the males and females gametes takes place inside the body of the female mate. It is a biological mechanism of sexual reproduction for this to happen the male mate has to release the sperms (male gamete) in the reproductive passage of the female mate. In mammals, reptiles, some fishes, some birds and animals this occurs by the means of copulation in which the male inserts the penis or any part of the external genitalia into the vagina, or cloaca or any other external genitalia of the female.
All humans are mammals and they reproduce by the means of internal fertilization. In this the male discharge the sperms by inserting the penis into the vagina of the female during copulation. The sperm cell fuses with the egg cell of the female and fertilization occurs in the body of the female.