All eukaryotic organisms contain cells with

A. chloroplasts.

B. a cell wall.

C. flagella.

D. a nucleus.

A nucleus

Explanation:

When you see any word with "kary" in it, it is referring to nucleus. So, the word eu-karyote actually means "new/with a nucleus."

Prokaryotes do not have nuclei, and this makes sense because their name means before (pro) nucleus. They came before the cells with nuclei.