For the identification of β-naphthol using dye test, it is necessary to use:

In an alkaline solution, $-\mathrm{OH}$ turns into $-{\mathrm{O}}^{-}$, which interacts with an azo molecule, such as  $\mathrm{Ph}-\mathrm{N}\equiv {\mathrm{N}}^{+}$, to produce an azo colour.
So, D is the right answer.