Find the missing letter in the series: B, D, F, H, ?

A. J

Which letter should replace the question mark in the series: B, D, F, H, ?

D. I

Complete the series: B, D, F, H, ?

A. J

Identify the missing letter in the series: Z, X, V, T, ?

C. Q

Complete the series: a, c, e, g, ?

B. H