The correct answer is A (I-spread) because the yield spread of a specific bond over the standard swap rate in the same currency and tenor is referred to as the I-spread or interpolated spread to the swap curve.

• B (Z-spread) is incorrect because the Z-spread represents a constant yield spread over a government or interest rate swap spot curve, not the swap rate. It is also known as the zero volatility spread.

• C (Option-adjusted spread) is incorrect because the option-adjusted spread (OAS) is derived from the Z-spread and is used for callable bonds, incorporating assumptions about future interest rate volatility.