Synonyms are words which have the same or nearly the same meaning in the same language.
Antonyms are words which have opposite meaning in comparison to the other.
Option B)purebred is correct as the word purebred means (of an animal or type of animal) with parents that are both of the same breedand the word hybrid means the offspring of two plants or animals of different species or varieties, such as a mule.
Both the words are opposite of each other.
The other options are not correct as they do not have the opposite meaning to the given word.