Pure line is true breeding genotypes, a line that has been rendered homozygous for all genes under consideration in successive generations, a line in which homozygous individuals is produce only homozygous offspring like parents. Thus, pure breed refers to homozygosity only. 

Homozygosity n independent assortment bcoz pureline breeds produce offspring of same phenotype...

Pureline breeds refer to
Pureline breeds are a type of breeding where individuals within a breed are homozygous for all traits. This means that they have identical alleles for a particular gene or set of genes. Pureline breeding is used to maintain the purity of a particular breed and to produce offspring that consistently exhibit the desired traits.

Homozygosity only
The correct answer is option 'A', which states that pureline breeds refer to homozygosity only. In pureline breeding, individuals are bred to be homozygous for all traits. This means that they have two identical alleles for each gene. Homozygosity is important because it ensures that the offspring will exhibit the desired traits consistently.

Explanation
Pureline breeding involves selecting individuals with desirable traits and breeding them together to produce offspring that will also have those traits. The process is repeated over multiple generations to establish a pureline breed.

During pureline breeding, individuals with different genotypes for a particular trait are not used. Instead, only individuals that are homozygous for the desired trait are selected for breeding. This ensures that the offspring will also be homozygous for the trait and will consistently exhibit the desired characteristics.

Homozygosity is important in pureline breeding because it reduces genetic variability within the breed. This allows for greater predictability in the traits exhibited by the offspring. By selecting homozygous individuals for breeding, breeders can ensure that the offspring will have the desired traits and characteristics.

In contrast, heterozygosity refers to having different alleles for a particular gene. If individuals with different genotypes for a trait are bred together, the resulting offspring will be heterozygous for that trait. This can lead to variation in the traits exhibited by the offspring, which is not desired in pureline breeding.

Therefore, pureline breeding refers specifically to homozygosity only. It is a breeding technique used to produce offspring that consistently exhibit the desired traits by selecting and breeding homozygous individuals.