Answer the following question given this paragraph: 

Protists are eukaryotes in the Protist Kingdom. Most are single-celled organisms. Protists are thought to be the oldest eukaryotes. They probably evolved when some prokaryotic cells invaded or were engulfed by others.


Q: What is thought to be the oldest eukaryotes?

 Choices:

- amoebas

- prokaryotes

- arthropods

- protists

A:
protists
