Answer: Callable bond

**Explanation:** - **Callable bonds** give the issuer the right to redeem the bond before maturity. When interest rates decline, issuers can call existing higher-coupon bonds and refinance at lower rates, reducing their interest expense. - **Putable bonds** benefit the investor, who can put (sell) the bond back to the issuer if rates rise. - **Extendible bonds** typically benefit investors by allowing them to extend the maturity. Therefore, callable bonds benefit issuers when interest rates decline.

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