The correct option is B 10
which the metal is di rectly at tached. Here, C2O2−4 is a bidentate ligand, and H2O is a monodentate ligand, So, total number of sites offered by C2O2−4 and H2O ligands around Th(IV)=Coordination number of Th(IV)
=4×2(by C2O2−4)+2×1(by H2O)=10