The most primitive monerans are

Options

(a) rickettsaie
(b) acitinomycetes
(c) progenote
(d) arachaebacteria

Correct Answer:

arachaebacteria

Explanation:

Archaebacteria are the oldest organisms living on the Earth. They are unicellular prokaryotes and belong to the kingdom, Archaea. They were first discovered in 1977 and classified as bacteria. Archaebacteria are found in very harsh conditions such as in the volcanic vents or at the bottom of the sea.