Find the missing letters in the series: b, d, f, h, ?

A. J

What letter should replace the question mark in the series: z, x, v, t, ?

A. R

Identify the missing letter in the series: m, n, o, p, ?

A. Q

Identify the missing letter in the series: m, n, p, q, ?

A. R

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

B. H