The total number of reagents from those given blow, that can convert nitrobenzene into aniline is ___________. (Integer answer)

I. Sn $-$ HCl

II. Sn $-$ NH₄OH

III. Fe $-$ HCl

IV. Zn $-$ HCl

V. H₂ $-$ Pd

VI. H₂ $-$ Raney Nickel