Which types of bonds or interactions are found in the β-helix of protein?

H-bond

The correct answer is Option (3) → H-bond

The β-structure (β-pleated sheet / β-helix) of proteins is a secondary structure stabilized mainly by hydrogen bonds formed between the –NH group of one peptide bond and the C=O group of another peptide bond.

Why others are incorrect:

• Ionic bond → mainly in tertiary structure 
• Covalent interaction → peptide bonds form primary structure 
• Banana bond → found in strained molecules like cyclopropane, not proteins 

Hence, the correct option is H-bond.