Biochemical Tests Identify Key Molecules

Steps:

• Benedict's test positive indicates reducing sugars present.
• Hydrolysis followed by Benedict's positive confirms non-reducing sugars.
• Biuret test positive shows proteins are in the mixture.
• Iodine test negative rules out starch.

Why C is correct:

• Option C matches tests for reducing sugars (Benedict's reaction with aldehyde groups), non-reducing sugars (post-hydrolysis reactivity), and proteins (Biuret's copper coordination with peptide bonds).

Why the others are wrong:

• A: Iodine test negative, so no starch.
• B: Biuret test positive, so proteins present.
• D: Benedict's positive, so reducing sugars present.

Final answer: C