Answer:
The correct answer is C. lack a nucleus
Step-by-step explanation:
Eubacteria are bacteria which is different from archaea but both archaea and bacteria are considered to be in prokaryotes however they both are divided into two different domain that is bacteria and archaea.
Bacteria and archaea are prokaryotes because they lack membrane-bound nucleus so their genetic material is scattered in the cytoplasm. Eukaryotes are organism which have their genetic material enclosed in a membrane-bound nucleus. So the similarity in archaea and eubacteria is that they both lack a nucleus.