Identifying biomolecules using specific chemical tests

Steps:

• Review test results for indicators of carbohydrates (e.g., iodine turns blue-black), fats (e.g., Sudan III stains red), and proteins (e.g., biuret turns violet).
• Check each powder: A shows positive for all three tests; B lacks fat test; C lacks protein test; D lacks carbohydrate test.
• Match the powder with positives across carbohydrate, fat, and protein columns in the table.
• Confirm only one powder meets all criteria.

Why A is correct:

• Powder A tests positive for all three biomolecules, matching the requirement for containing carbohydrate, fat, and protein per standard biochemical identification tests.

Why the others are wrong:

• B: Negative for fat test, so lacks fat.
• C: Negative for protein test, so lacks protein.
• D: Negative for carbohydrate test, so lacks carbohydrate.

Final answer: A