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

A. R

What letter comes next in the series: M, O, Q, S, ?

B. T

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

A. I

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

A. O

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

A. J