Interpreting biochemical test results for sugars and starch

Steps:

• Iodine test shows blue-black color, confirming starch presence.
• Benedict's test on original solution is negative (no red precipitate), ruling out reducing sugars.
• After acid hydrolysis, Benedict's test turns positive, indicating non-reducing sugars.
• Biuret test is negative (no violet color), confirming no proteins.

Why A is correct:

• Non-reducing sugars give negative Benedict's initially but positive after hydrolysis (breaking into reducing monosaccharides), and starch tests positive with iodine.

Why the others are wrong:

• B: Includes protein, but Biuret test is negative.
• C: Includes reducing sugar, but initial Benedict's test is negative.
• D: Omits non-reducing sugar, but hydrolysis confirms its presence.

Final answer: A