Step 1: Idea behind the question
A collateral security is a pledge, so the debentures are recorded only to show the lender's claim. On repayment of the loan, the books must go back to the position before the pledge.
Step 2: Reasoning with the accounts
At issue the two accounts moved as follows: Debenture Suspense went up on the debit side and % Debentures went up on the credit side.
To undo this, % Debentures must come down, so it is debited. Debenture Suspense must come down too, so it is credited.
Step 3: Test each option against this rule
Option 1 has a Bank credit, but no money is paid, so it is out.
Option 2 repeats the issue entry, so it is out.
Option 4 shows a cash receipt from debenture holders, which never happened, so it is out.
Only option 3 debits % Debentures and credits Debenture Suspense.
Step 4: Conclusion
Option 3 is the reversal of the issue entry and is the correct cancellation entry.
Final Answer:
The correct entry is % Debentures A/c Dr. To Debenture Suspense A/c.
\[ \boxed{\text{Option 3}} \]