There are currently millions of species of single-celled organisms, and million of others that were once here and are now extinct. which of these would best describe the first, most primitive organism to arise on earth from which all other life evolved? . a). unicellular eukaryote. b). unicellular prokaryote. c). multicellular eukaryote. d). multicellular prokaryote

The answer is  : B

in order to answer this question, we just need to find out which organism has the simplest form

Unicellular  (organism that has only 1 cell) is more simple than multicellular so it eliminate option C and D

Prokaryote is more simple than eukaryote since prokaryote organism hasn't developed nucleus which make than organism could run complex activities. This eliminate option A

hope this helps