Answer the following question given this paragraph: 

Not all archaeans live in extreme conditions. In fact, archaeans are now known to live just about everywhere on Earth. They make up as much as 20 percent of Earth's total mass of living things.


Q: What kingdom of organisms constitutes up to 20 percent of all living things on earth in mass?

 Choices:

- protists

- sporozoans

- vertebrates

- archaeans

A:
archaeans
