In 1735 Carlous Linneaus a Botanist said that there needs to be a way to classify organisms and living things. He decided that he'll sort organisms into seven major taxa, or groupings. He called the highest taxa kingdom and the lowest taxa species. This is known as the first idea in the process of Linnaean Taxonomy.
Then in 1990 Carl Wossen a microbiologist and biophysicist added to this idea saying that he Linnaean taxonomy works well, but it could be better. Thta there could be a better way into classifying and grouping kingdoms. He then created 3 domains: Bacteria, Archaea, and Eukarya, aka, regular bacteria, extreme bacteria, and everything else.
This furthermore is the method we use in classifying living things.
The answer is: B, Domain.