(N/A) The various methods to avoid pregnancy (contraception) include:
$(i)$ Barrier methods (e.g.,condoms) to prevent physical contact between sperm and egg.
$(ii)$ Chemical methods (e.g.,oral pills) which change the hormonal balance of the body to prevent the release of an egg (ovulation).
$(iii)$ Intrauterine devices (e.g.,copper $T$ or loop) which are placed in the uterus to prevent implantation.
$(iv)$ Surgical methods (e.g.,vasectomy in males or tubectomy in females) which block the vas deferens or fallopian tubes respectively.
Elaboration of Chemical Method (Oral Pills):
Oral contraceptive pills contain specific hormones that inhibit the release of eggs from the ovaries. By preventing ovulation,the sperm has no egg to fertilize,thereby effectively preventing pregnancy.