Final answer:
The vending source that enables investors to convert their investment into a certain number of company shares is the convertible bond, chosen for its dual benefits of fixed-interest payments and the possibility of owning stock.
Step-by-step explanation:
The vending source that allows investors to convert into a specific amount of shares of the company stock is c. Convertible Bonds. A convertible bond is a type of financial security that is a bond, but that can be converted into a determined number of shares of the company's stock. This provides investors with the safety of receiving fixed-interest payments with the bond, but also gives them the opportunity to convert the bond into stock, which can potentially increase in value, giving the investor a stake in the company's ownership and potential voting rights.