Step 1: Different methods of redemption.
- Conversion: Debentures can be redeemed by converting them into shares or new debentures.
- Instalments: Debentures may be redeemed gradually over time in instalments.
- Lumpsum: Debentures can also be redeemed by a one-time lumpsum payment at maturity.
Step 2: Conclude.
Since all the mentioned methods are valid, the correct option is “All of these”.
Final Answer:
\[
\boxed{\text{All of these}}
\]