Answer:
a. a membrane-bound nucleus
d. presence of mitochondria or chloroplasts
Step-by-step explanation:
Procaryotes are the organisms that lack membrane-bound well-defined nucleus in their cells. These organisms have their DNA present in the cytoplasm itself. Procaryotes also lack the membrane-bound organelles such as mitochondria, chloroplasts, Golgi apparatus, etc.
On the other hand, eucaryotes have a membrane-bound well-defined nucleus in their cells to house DNA in it. These organisms also have membrane-bound organelles in their cells. Examples of procaryotes are bacteria and archaea while animals and plants are eucaryotes.