Concept:A loan to a company under the company's seal is formally recognised as a debenture.
Explanation:A debenture is a written document issued by a company under its seal that acknowledges a debt owed to the lender.
The phrase "under the company's seal" indicates that the loan is supported by a legally binding formal instrument.
Fixed deposits are bank investments, not loans to a company under seal.
A mortgage involves a specific property interest as security for a loan, but it is not the general term for a company loan under seal.
A bond is a security, but in corporate accounting, the instrument that a company seals to acknowledge a loan is called a debenture.
Therefore, the correct answer is the option for debenture.
Answer:D. Debenture