Find the incorrect pair.

Question

$\begin{array}{1 1} (a)\;\text{Leech-Phylum Annelida} \\ (b)\; \text{Octopus-Phylum Mollusca} \\ (c)\; \text{Liverfluke-phylum platyhelminthes} \\ (d)\; \text{Star fish-Phylum Chordata} \end{array}$