You have discovered a new coccoid-shaped microorganism with no nucleus, a rigid cell wall, and a diameter of 2 μm. chemical tests reveal that its cell wall does not contain peptidoglycan. the new microorganism is.
a) most likely a bacterium.
b) most likely a eukaryote.
d) either a bacterium or an archaeon

C) Most likely an archaeon

Explanation:

Because this new microorganism has a rigid cell wall but lacks of peptidoglycan it is very likely that this is not a bacterium; bacterial cell walls are made of peptidoglycan.  

This new microorganism cannot be an eukaryote either because all eukaryotes have a nucleus in their cells.

It is possible that the new microorganism is an archeon (belongs to the Archea domain) because organisms within Archea have cell walls assembled from surface-layer proteins. Also, Archaea and bacteria are generally similar in size and shape including  2 μm microorganism and coccoid shapes.

answer; the tunica intima also called tunica interna, consists of elastic fibers,connective tissue and smooth muscle cells;