Non-membrane bound structures in prokaryotes are
A) Ribosomes  
B) Inclusion bodies 
C) Nucleolus
D) Microtubules 

Non-membrane bound structures found in prokaryotes are ribosomes, inclusion bodies, nucleoid, plasmids etc. Nucleolus is also a non-membrane bound structure, but it is found in eukaryotes. Microtubules are part of the cytoskeleton found in eukaryotes. They are not bound by membrane.