Which of the following statements is (are) true with respect to the price behavior of putable bonds?
I). At very high levels of interest rates, the price of a putable bond will be very close to that of an equivalent non-putable bond.
II). At very low levels of interest rates, the put embedded in the bond will have a very low value.
III). Negative convexity will begin to appear for a putable bond at very low yield levels.
IV). At high yield levels, duration will underestimate the expected bond price for a given unit change in yield.