Last Year, You Created an Immunized Portfolio with an Average

Last year, you created an immunized portfolio with an average maturity date of 14.5 years, a yield to maturity of 9.8%, and a duration of 9.6 years. According to the policy of dynamic immunization, which of the following is the best choice for modifying your portfolio?

A) modify the yield to maturity to 9.1%
B) modify the portfolio so the average maturity remains at 14.5 years
C) modify the portfolio so the average maturity becomes 13.5 years
D) modify the portfolio so the duration remains at 9.6 years
E) modify the portfolio so the duration becomes 8.6 years