Which one of the following compounds shows the presence of intramolecular hydrogen bond ?

The compound that will react most readily with gaseous bromine has the formula :

Which among the give nmolecules can exhibit tautomerism?

The correct structure of the product A formed in the reaction:

Consider the reaction :

CH₃CH₂CH₂Br + NaCN  → CH₃CH₂CH₂CN + NaBr

This reaction will be the fastest in :

A given nitrogen-containing aromatic compound A reacts with Sn/HCl, followed by HNO₂ to give an unstable compound B. B, on treatment with phenol, forms a beautiful coloured compound C with the molecular formula C₁₂H₁₀N₂O. The structure of compound A is :