Inbreeding is carried out in animal husbandry because it:

Increase homozygosity

The correct answer is Option (4)- Increase homozygosity

A group of animals related by descent and similar in most characters like general appearance, features, size, configuration, etc., are said to belong to a breed.

When breeding is between animals of the same breed it is called inbreeding, while crosses between different breeds are called outbreeding.

Inbreeding : Inbreeding refers to the mating of more closely related individuals within the same breed for 4- 6 generations. The breeding strategy is as follows – superior males and superior females of the same breed are identified and mated in pairs. The progeny obtained from such matings are evaluated and superior males and females among them are identified for further mating. A superior female, in the case of cattle, is the cow or buffalo that produces more milk per lactation. On the other hand, a superior male is the bull, which gives rise to superior progeny as compared to those of other males. Inbreeding increases homozygosity. Thus inbreeding is necessary if we want to evolve a pureline in any animal.