Amoebas are unicellular organisms, while human beings are multi-cellular and the most intelligent of organisms. however, both are classified as eukaryotes. how will you justify this reasoning? .

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.

"do a testcross with a homozygous recessive plant."

this age may represent the age of the earth's accretion, of core formation, or of the material from which the earth formed. this dating is based on evidence from radiometric age-dating of meteorite material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.