Which of the following statements is incorrect? Pls explain your answer.

a. The duration of a coupon bond maturing at date T is always less than the duration of a zero coupon bond maturing on the same date.

b. The modified duration of a bond is always less than the Macaulay duration of the same bond if interest rates is positive.

c. To measure the price sensitivity of a callable bond to the change of interest rates, one needs to calculate the bonds modified duration.

d. Embedded option of a bond reduces its effective duration.