Biochemical tests identify reducing sugars and lipids

Steps:

• Benedict's test produces brick-red precipitate with reducing sugars due to reduction of Cu²⁺ to Cu₂O.
• Ethanol emulsion test turns cloudy when lipids dissolve in ethanol and form an emulsion in water.
• Brick-red result confirms reducing sugars; cloudiness confirms lipids.
• No other tests mentioned, so sample contains only these molecules.

Why A is correct:

• Benedict's detects reducing sugars (e.g., glucose) via color change; ethanol test detects lipids via emulsion, matching both observations.

Why the others are wrong:

• B: No test (e.g., biuret) indicates proteins.
• C: Starch gives no Benedict's reaction; no protein test.
• D: Non-reducing sugars (e.g., sucrose) yield no Benedict's color change.

Final answer: A