Preferred stock may include convertible features that allow holders to exchange the preferred shares for another security of the issuing company—most commonly common stock—at a specified conversion ratio. That is why choice B is correct. Convertible preferred combines characteristics of equity income (a stated dividend) with the potential upside participation of common stock through the conversion privilege. The conversion feature is set by the issuer and described in the security’s terms at issuance.

Choice A is not the best answer because “common stock” itself is not typically described as “convertible” into other company issues; conversion features are commonly attached to preferred stock or bonds (convertible debentures), not standard common shares. Choice C, commercial paper, is a short-term unsecured corporate money market instrument; it is not typically issued with conversion features—its hallmark is short maturity and credit quality, not embedded equity options. Choice D, an ETF, is an investment company product whose shares represent an interest in a portfolio; ETFs are not typically “convertible” into other issues of the company in the way convertible preferred is.

This is a product-knowledge question aimed at understanding embedded features and how issuers structure securities. For SIE purposes, remember: convertibility is most commonly associated with preferred stock and certain corporate bonds, and it provides investors with an option-like feature that can change the security’s risk/return profile (income plus potential appreciation).