• In case of phosphonic acid (iii) H₃PO₂ it reduces benzene and the diazonium group gets replaced by hydrogen and itself oxidizes to H₃PO₃.

• benzenediazonium chloride participates in de-amination reaction with (ii) CH₃CH₂OH . it converts to bezene and as side products acetaldehyde , nitrogen and HCl gas is formed.

• Options (i) and (iv) are incorrect.