James has a 10 year investment horizon. To achieve an immunized position, his bond portfolio will have an average duration that is: O a. less than 10 years and have an average maturity that is equal to 10 years. O b. equal to 10 years and have an average maturity that is greater than 10 years. O c. greater than 10 years and have an average maturity that is less than 10 years. O d. equal to 10 years and have an average maturity that is less than 10 years