In an antibody, disulphide bonds are present __________
i. between two heavy chains
ii. between two light chains
iii. between the constant region of light chain and the constant region of a heavy chain and light chains
iv. between antigen binding sites of both the heavy and light chains
v. between the variable region of light chain and that of heavy chain
Select the correct answer from the options given below

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.