Explanation:

When a tripeptide is treated with Sanger's reagent, it reacts with the α-amino group of the N-terminal amino acid to form a phenylthiocarbamoyl (PTC) derivative. This reaction is specific for the N-terminal amino acid and does not react with the side chains of other amino acids in the peptide chain.

Hydrolysis of the PTC derivative:
After the Sanger's reaction, the PTC derivative is hydrolyzed to release the phenylthiocarbamoyl (PTC) group from the N-terminal amino acid. This hydrolysis step is usually carried out using concentrated hydrochloric acid.

Identification of the hydrolyzed amide bonds:
To determine the number of amide bonds hydrolyzed in the peptide chain, we need to analyze the products formed after hydrolysis. The PTC group is cleaved from the N-terminal amino acid, leaving behind a free N-terminal amino group. Since the Sanger's reagent specifically reacts with the N-terminal amino group, only the first amide bond in the peptide chain is hydrolyzed.

Example:
Let's consider a tripeptide sequence: Ala-Gly-Leu. After treatment with Sanger's reagent and hydrolysis, the products obtained are:

- PTC derivative of Ala-Gly-Leu
- Free N-terminal amino group of Gly-Leu (with the PTC group removed)

In this example, the amide bond between Ala and Gly is hydrolyzed, resulting in the release of the N-terminal amino group of Gly-Leu. The amide bond between Gly and Leu remains intact since the Sanger's reagent does not react with the side chains of amino acids.

Conclusion:
In conclusion, when a tripeptide is treated with Sanger's reagent followed by hydrolysis, only the N-terminal amide bond is hydrolyzed. Therefore, the correct answer is '2', indicating that two amide bonds will be hydrolyzed in the peptide chain.