Answer :
Unicellular organisms have all the necessary cell organelles and a well-defined nucleus, therefore fulfilling the characteristics of eukaryotes.
Answer:
All the organisms are divided into prokaryotes and eukaryotes. Prokaryotes contain the organisms that are single celled and do not have membrane-bound nucleus and other membrane-bound organelle.
Eukaryotes can be single cellular like amoeba or multicellular like humans but all the eukaryotes contain a membrane-bound nucleus in which their genetic material is packed and enclosed and other membrane-bound organelles are also present.
As amoeba have a membrane-bound nucleus which contains its genetic material, therefore, they are considered in eukaryotes. So eukaryotes contain those organisms which have membrane-bound organelle like nucleus and they can be unicellular or multicellular.