Step 1: Understand the basis of the question:
The question asks about security. Does the debenture have a specific charge on the assets of the company or not?
Step 2: Recall the types:
Secured (mortgage) debentures have a specific charge on assets.
Unsecured (naked) debentures have no such charge. The holders are only ordinary creditors.
Step 3: Pick the option:
No specific charge on assets means unsecured debentures, option (C).
Step 4: Why the other options are wrong:
(A) Non-convertible debentures cannot be changed into shares. This is about conversion, not security.
(B) Irredeemable debentures are not repaid during the life of the company. This is about repayment.
(D) Bearer debentures pass by delivery and no holder record is kept. This is about transfer.
Final Answer:
The answer is unsecured debentures, option (C).