How many $EDTA$ molecules are required to form an octahedral complex with a $Ca^{2+}$ ion?

One mole of the octahedral complex compound $Co(NH_3)_5Cl_3$ gives $3$ moles of ions on dissolution in water. One mole of the same complex reacts with excess of $AgNO_3$ solution to yield two moles of $AgCl_{(s)}$. The structure of the complex is :

The coordination number of aluminum in its common complexes is

Which of the following ligands is not bidentate?

In which of the following compounds,the transition metal is in an oxidation state of zero?

In the coordination complex $[E(en)_2(C_2O_4)]NO_2$,the coordination number and oxidation state of $E$ are respectively: