Which of the following is an insoluble porous cross-linked polymer of enormous strength and rigidity present only in prokaryotes?

Peptidoglycan, also known as murein, is a polymer consisting of sugars and amino acids that forms a mesh-like layer outside the plasma membrane of bacteria forming the cell wall. Peptidoglycan serves a structural role in the bacterial cell wall by giving structural strength as well as counteracting the osmotic pressure of the cytoplasm.