Concept:Internal finance is generated from within the business itself.
Explanation:Retained earning is the profit kept in the business after paying dividends to shareholders.
This profit belongs to the business and is available for reinvestment.
It is an internal source because no outside party is involved.
Trade credit is a facility provided by suppliers, so it is an external source.
An overdraft is a borrowing facility from a bank, so it is also external.
A debenture is a loan taken from investors, making it an external source as well.
Therefore, among the given options, only retained earning is generated internally.
Answer:B. retained earning