a callable bond issuer will recall their bonds only when interest rates....... A puttable bond allows investors to sell their bonds back to the issuer only when interest rates $......$ Note: A callable bond is a bond that allows issuers to redeem or buy back outstanding bonds before the matuirty date. A puttable bond is a bond that allows investors$/$bond buyers to sell back their bonds to issuers before the maturity date.

a$)$ decrease beyond a threshold; decrease beyond a threshold

b$)$ increase beyond a threshold$/$ increase beyond a threshold

c$)$ increase beyond a threshold; decrease beyond a threshold

d$)$ decrease beyond a threshold; increase beyond a threshold