Please help me with 26 and 27

E. 3.74% 26. A perfectly indexed portfolio will underperform the benchmark index because of A. index duration lag B. index convexity lag C. duration risks D. convexity risks E. transaction costs 27. The bond immunization strategy for a single liability is to: A. match the average duration of the bonds with the time horizon of the liability B. match the average maturity of the bonds with the time horizon of the liability C. match the dollar duration of the bond portfolio with the amount of the liability D. match the yield to maturity of the bond portfolio with the discount rate of the liability E. ensure that average maturity of the bonds is higher than the time horizon of the liability