When debentures are issued as security against a loan then such as issue of debentures is called:

Secured
Partly secured
Collateral security
Bilateral security

The correct answer is: A. Secured

A secured debenture is a type of debenture that is backed by collateral. This means that the lender has the right to seize the collateral if the borrower defaults on the loan. Collateral can be anything of value, such as real estate, equipment, or inventory.

A partly secured debenture is a type of debenture that is only partially backed by collateral. This means that the lender does not have the right to seize all of the collateral if the borrower defaults on the loan.

Collateral security is a type of security that is used to guarantee the repayment of a loan. This type of security can be anything of value, such as real estate, equipment, or inventory.

Bilateral security is a type of security that is used to guarantee the performance of a contract. This type of security can be anything of value, such as a bond or a letter of credit.

In conclusion, the correct answer is: A. Secured.