The correct answer is c) Archaea.
Archaea are unique among microorganisms as they often have a cell membrane structure that can feature a monolayer composition, particularly in extreme environments. Unlike bacteria and eukaryotes, which typically have a lipid bilayer in their membranes, certain archaea possess a single-layer membrane that consists of ether-linked lipids. This monolayer structure provides enhanced stability and rigidity, making it advantageous for survival in harsh conditions such as high temperatures and acidity.
Viruses, on the other hand, are not classified based on their cell membrane structure as they do not have a cell membrane per se; they are not considered living cells. Yeast, classified as eukaryotes, also do not contain a monolayer in their membranes, as they have a bilayer structure similar to that of other eukaryotic cells. Therefore, when considering the question of which microorganism can have a monolayer in its cell membrane, archaea are the only group that fits this description.