Decarboxylation of all six possible forms of diaminobenzoic acids \( \mathrm{C_6H_3(NH_2)_2COOH} \) yields three products A, B and C. Three acids gives a product ‘A’, two acids gives a product ‘B’ and one acid give a product ‘C’. The melting point of product ‘C’ is
The reagent, from the following, which converts benzoic acid to benzaldehyde in one step is: 
