(i) Administration of progestogens or progestogen estrogen combinations or IUDs within 72 hours of coitus.
(ii) Progestogens alone or in combination with estrogen inhibit implantation as well as alter the quality of cervical mucus to prevent the entry of sperms.
IUDs increase the phagocytosis of sperms within the uterus, suppress sperm motility and fertilising capacity of sperms.
(iii) No, STDs can be prevented by use of condoms.
(iv) Gonads are endocrine glands and thus cannot be removed from the body.