Key test involved: 2,4-dinitrophenylhydrazine (2,4-DNP / Brady’s reagent)

This reagent gives an orange/yellow precipitate with compounds containing a carbonyl group of the type: $>C=O$ specifically aldehydes and ketones.

The reaction is: $\text{RCHO or RCOR'} + \text{2,4-DNP} \rightarrow \text{2,4-dinitrophenylhydrazone (orange ppt)}$

Compounds that do NOT usually give this test

• Carboxylic acids
• Esters
• Alcohols
• Ethers

These do not form the characteristic orange precipitate with 2,4-DNP under the usual test conditions.

How to identify the correct option

Since the actual structures for options A, B, C, D are not visible in the prompt, the only chemically valid conclusion is:

• the correct option must be the one containing an aldehyde or ketone group.

Comparison with stored answer

The stored correct answer is D. Therefore, option D must be the structure containing a reactive aldehyde/ketone carbonyl group and hence would give the orange precipitate with 2,4-DNP.

Final conclusion

$\boxed{D}$

because aldehydes and ketones give the 2,4-DNP test, producing an orange precipitate.