This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Structure and function of protein, Subject name: Biochemistry
Covalent bond is seen in 
Select and explain. 
A. Hydrogen bond, B. Disulphide bond, C. Electrostatic bond, D. Ionic bond
B: Disulphide bond
Answer: B: Disulphide bond 
Explanation: Disulphide bonds: These are formed between two cysteine residues. They are strong, high energy covalent bonds.Ref: Textbook of medical biochemistry, MN Chatterji, 8th edition, page no: 89