$\mathrm{Zn}(\mathrm{OH}{)}_2\downarrow$ is soluble in :

Zinc hydroxide is soluble in  sodium hydroxide, ammonia solution and ammonium salt.

Since zinc hydroxide generally has water ligands around its ion, it dissolves when too much sodium hydroxide is introduced to the solution. This happens because the hydroxide ions lower the complex to a charge and make the compound soluble.

In excess of ammonium hydroxide, the precipitated zinc hydroxide is soluble. A colorless, water-soluble ammine compound is formed.

Zinc hydroxide dissolves in aqueous ammonia to produce an ammine complex, which is a white liquid

The hydroxide ions that separate from $\mathrm{Zn}(\mathrm{OH}{)}_2$ when ammonia is introduced in excess react with it to form a positively charged tetra complex with a co-ordination number of four.

Hence, the option D is correct.