Homozygous purelines in cattle can be obtained by Mating of individuals of different species, Mating of individuals of different breed, Mating of related individuals of same breed, Mating of unrelated individuals of same breed

The correct option is B. Mating of related individuals of same breed. Pureline selection is the ability to select the superior individual to develop and improve a particular trait. The homozygous genes are selected to improve a particular trait by mating of related individuals of the same breed. So, the correct answer is option B.