Answer:
Option A , Prokaryotes
Explanation:
The simplest form of life existing on earth is the prokaryotes. Prokaryotes have a single celled structure which does not contain an individual nucleus. Also it has no membrane bound organelles. There are several organelles which are not even present in prokaryotes as compared to a eukaryotic cell. They have a simple chromosome that is circular in shape
Prokaryotes include bacteria and archaes
Hence, option A is correct
