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

In gaseous triethyl amine the "$$-$$C$$-$$N$$-$$C$$-$$" bond angle is _________ degree.

The number of nitrogen atoms in a semicarbazone molecule of acetone is ______________.