If the value of the IO strip is most sensitive to changes in the market rate when this rate is between 100 and 300 basis points below the coupon on the pool, then those investors who desire to obtain the hedging benefits of the IO strip should purchase:

a. strips of passthroughs 100-300 points below the market rate

b. only strips of passthroughs at the market rate

c. strips of passthroughs 100-300 points above the market rate

d. only PO strips 100-300 points below the market rate