Which of the following is not a source of capital to a sole proprietor?

The option that is not a source of capital to a sole proprietor is borrowing through debentures. Debentures are long-term financial instruments used by companies to raise capital by borrowing from the public. They are essentially loans that a company borrows from investors, promising to repay the principal amount along with interest at a specified rate. Sole proprietors, who run businesses on their own, are not allowed to issue debentures as a means of raising capital. Therefore, borrowing through debentures is not a source of capital available to sole proprietors.