Which among the following is a monodentate ligand?

Which complex among the following gives a white precipitate on treatment with an aqueous solution of barium chloride?

Which of the following complexes is homoleptic?

Which of the following statements is true about $[Cu(NH_3)_4]SO_4$?

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

Which of the following is a common donor atom in ligands?