A, B and C are three biomolecules. The results of the tests performed on them are given below:

	Molisch's test	Barfoed Test	Biuret Test
A	Positive	Negative	Negative
B	Positive	Positive	Negative
C	Negative	Negative	Positive

A, B and C are respectively:

First, recall what each of the three qualitative tests tells us.

Molisch’s test detects any carbohydrate. If a substance gives a violet ring with α-naphthol and concentrated H2SO4, the test is said to be positive, so the substance must be a carbohydrate. If the test is negative, the substance is not a carbohydrate.

Barfoed’s test distinguishes between monosaccharides and disaccharides. Monosaccharides reduce Cu2+ of Barfoed’s reagent to red Cu2O within about 2-3 minutes, so the test becomes positive. Disaccharides react much more slowly, so in the usual test time they give a negative result.

Biuret test identifies compounds that contain two or more peptide (-CO-NH-) bonds. Proteins and polypeptides give a violet colour, i.e. a positive test, because they have many peptide bonds. Simple amino acids possess no peptide bond at all, so their Biuret test is negative.

Now examine each unknown biomolecule in turn.

Substance A gives Molisch positive, Barfoed negative, Biuret negative. We have:   • Molisch positive ⇒ A is a carbohydrate.   • Barfoed negative ⇒ A is not a monosaccharide; therefore it must be a disaccharide.   • Biuret negative ⇒ A has no peptide bonds, confirming it is not a protein. Among the options, the only disaccharide offered is lactose. Hence $$A = \text{Lactose}.$$

Substance B shows Molisch positive, Barfoed positive, Biuret negative. We have:   • Molisch positive ⇒ B is a carbohydrate.   • Barfoed positive ⇒ B is a monosaccharide.   • Biuret negative ⇒ B is not a protein. Both glucose and fructose are reducing monosaccharides, so either could in principle satisfy the first two tests. However, in the list of answers that already matches A (lactose) and C (to be decided next), the only consistent monosaccharide offered is glucose. Thus we assign $$B = \text{Glucose}.$$

Substance C gives Molisch negative but Biuret positive. We have:   • Molisch negative ⇒ C is not a carbohydrate.   • Biuret positive ⇒ C must contain many peptide bonds, i.e. it is a protein. Albumin is a well-known protein, whereas alanine is only a single amino acid (no peptide bond), so alanine would give Biuret negative. Therefore $$C = \text{Albumin}.$$

Collecting the three identifications, we find

$$A = \text{Lactose},\quad B = \text{Glucose},\quad C = \text{Albumin}.$$

Comparing with the options, we match Option 2.

Hence, the correct answer is Option 2.