A. Algin (alginates) is characteristic of brown algae (Phaeophyceae) such as \emph{Laminaria} \(\Rightarrow A\!-\!IV.\)
B. Polysulphated esters (sulphated polysaccharides) are typical of many red algae (Rhodophyceae) like \emph{Polysiphonia} \(\Rightarrow B\!-\!III.\)
C. Chitin is the major structural polymer in fungal cell walls — \emph{Neurospora} is a fungus \(\Rightarrow C\!-\!II.\)
D. Murein (peptidoglycan, often called murin) is found in eubacterial cell walls (Eubacterium) \(\Rightarrow D\!-\!I.\)
Thus the correct matching is \(A\!-\!IV,\ B\!-\!III,\ C\!-\!II,\ D\!-\!I\) — option (3).