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

A. J

What is the next letter in the series: A, C, E, G, ?

B. H

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

D. I

What comes next in the series: M, N, O, P, ?

A. Q

What is the next letter in the series: B, E, I, M, ?

A. O