A bond with negative convexity is best described as having a price-yield relationship displaying:

a. Positive convexity at high yields and negative convexity at low yields.

b. Negative convexity at high yields and positive convexity at low yields.

c. Negative convexity at low and high yields and positive convexity at medium yields.

d. Positive convexity at low and high yields and negative convexity at medium yields.