The domain that contains both unicellular and multicellular organisms is Eukarya.

Here's why:

* Eukarya includes organisms with cells that have a nucleus and other membrane-bound organelles. This domain encompasses a wide diversity of life forms, from single-celled protists like amoebas to complex multicellular organisms like plants, animals, and fungi.

* Bacteria and Archaea are both prokaryotic domains, meaning their cells lack a nucleus and other membrane-bound organelles. All members of these domains are unicellular.

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