A group of animals which are related by descent and share many similarities are referred to as:

Breed is a group of animals that have similar appearance and behaviour and can be easily distinguished from other organisms. Example: American saddlebred and Arabian breed of horses etc.

Race is a genetically distinct population of individuals within the same species. Example: white race, black race etc in Homo sapiens.

Variety is a taxonomic rank below species. In variety the member of the same species have very minor difference. Example: white, red, pink etc variety of roses.

Species is a group of closely related organism (individuals) that are similar and are capable of interbreeding. Example: sapiens and erectus species of genus Homo.

Hence, due to above reasons the answer is breed.