How many of the given compounds will give a positive Biuret test? ______
Glycine, Glycylalanine, Tripeptide, Biuret

The Biuret test is positive for compounds that contain two or more peptide bonds (amide linkages), or the compound biuret itself, which has a similar structural motif.

Since glycine is a single amino acid with no peptide bonds, it does not give a positive Biuret test, and similarly glycylalanine, being a dipeptide with only one peptide bond, also fails to produce a positive result because at least two peptide bonds are required.

On the other hand, a tripeptide contains two peptide bonds and therefore gives a positive Biuret test; likewise, biuret (H$$_2$$N-CO-NH-CO-NH$$_2$$) has two amide linkages analogous to peptide bonds and also yields a positive result.

From the above, two compounds (the tripeptide and biuret) give a positive Biuret test, so the answer is 2.