Why is it difficult to classify some bacteria and archaea from each other?

What the theory that the sun goes around earth was replaced with the theory that earth goes around the sun this was an exaple of a

1. watermelon, papaya, oranges, bananas, and lemons are included in this food group. vitamin c 2. you need 6 or more servings of this food group each day vitamins d and a 3. found in fruit and keeps blood vessels healthy calcium 4. vitamins found in milk bread and grain 5. a mineral that strengthens bones fruit

The science for classifying and naming organisms is known as