Corporate bonds are most directly impacted by credit risk, making A the correct answer. Credit risk is the risk that the issuer will be unable to meet its promised obligations—specifically, the ability to make timely interest payments and repay principal at maturity. Because corporate issuers are private-sector entities, they carry a meaningful possibility of financial distress, earnings deterioration, increased leverage, or bankruptcy—factors that can widen credit spreads and push bond prices down.

While interest rate risk affects all fixed-income securities, corporate bonds have an added layer of valuation sensitivity: changes in the issuer’s perceived creditworthiness can significantly change the bond’s yield and market price, even if Treasury yields are stable. This is why corporate bonds are commonly evaluated using credit ratings, spreads versus Treasuries, and issuer financial strength metrics.

Choice B (political risk) may affect certain industries more than others, but it is not the defining risk type for corporate bonds overall. Choice C (liquidity risk) can matter—some corporate issues trade less frequently than Treasuries—but liquidity is typically not the primary driver compared with the issuer’s credit profile. Choice D (currency risk) is relevant mainly when investing in bonds denominated in foreign currencies or when the investor’s base currency differs from the bond’s currency. Standard U.S. corporate bonds denominated in dollars generally do not expose a U.S. investor to currency risk.

On the SIE, this is a foundational comparison: Treasuries = lowest credit risk, municipals depend on issuer/tax base or revenue pledge, and corporates = higher credit risk, often compensated by higher yields.