Interpret each test result

We are given:

• 2,4-DNP test: coloured precipitate
• Iodoform test: yellow precipitate
• Azo-dye test: no dye formation

Inference from 2,4-DNP test

The $2,4$-dinitrophenylhydrazine test is given by aldehydes and ketones.

So, compound $X$ must contain a carbonyl group $\left(>C=O\right)$ of an aldehyde or ketone.

Inference from iodoform test

A positive iodoform test is given by compounds containing either:

• the methyl ketone group, $\ce{CH3CO-}$, or
• alcohols of type $\ce{CH3CH(OH)-}$, which get oxidized to methyl ketones.

But from step 2, since $X$ already gives 2,4-DNP, it must itself be a carbonyl compound, not just an alcohol.

Therefore, $X$ should be a methyl ketone: $\ce{R-CO-CH3}$

Inference from azo-dye test

The azo-dye test is given by phenols (and certain aromatic amines after diazotization/coupling).

Since there is no dye formation, $X$ is not a phenol.

Combine all observations

So $X$ must be:

• a ketone,
• specifically a methyl ketone,
• and not a phenol.

Hence the correct option must be the one corresponding to a simple methyl ketone such as acetone / methyl ketone, which is given as Option B.

Conclusion

Therefore, compound $X$ is Option B.