Select the letter from among the given options that can replace the question mark (?) in the following series. E, F, I, N, U, ?

A D N Z

D

E, F, I, N, U, ? The difference between consecutive terms is increasing odd numbers, such that:   The logic followed here is : E → (+1) → F → (+3) →I → (+5) →N → (+7) → U → (+9) → D