Homozygous purelines in cattle can be obtained by:
mating of related individuals of same breed
mating of unrelated individuals of same breed
mating of individuals of different breed
mating of individuals of different species
Homozygous pure lines can be obtained by mating related individuals of the same breed.
Inbreeding is defined as the mating of related individuals of the same breed for 4-6 generations. hence correct option is (1).