Functional group identification via chemical tests Steps:

• Complete combustion to CO2 and H2O indicates T contains C, H, and possibly O, but no N, S, or halogens.
• Steamy fumes with PCl5 confirm presence of -OH group (alcohols or carboxylic acids react to form HCl).
• No visible product with 2,4-DNPH rules out aldehydes and ketones (test specific for those carbonyls).
• Carboxylic acids have -COOH (includes -OH) but their carbonyl does not react with 2,4-DNPH, so both alcohols and carboxylic acids fit all tests.

Why D is correct:

• Not applicable; tests contradict aldehyde (would react with 2,4-DNPH).

Why the others are wrong:

• A: Possible but not certain (could be alcohol instead).
• B: No -OH, so no PCl5 reaction.
• C: Possible but not certain (could be carboxylic acid instead).

Not enough information. Final answer: Not enough information.