Answer: C. puttable
Explanation:
A puttable bond is known as a type of bond which permits the holder to use the element of force on the issuer to repay the bond at an agreed price during a specified period of time before its maturity date. In other word, it guarantees the holder the right to get early refund before the bond matures and it is of great benefit to investors because it guard them against high interest rate. Thus, it is also known as a put bond.