Identify the missing letter: a, e, i, o, ?

A. U

Complete the series: m, n, o, p, ?

A. Q

Complete the series: m, n, o, p, ?

A. Q

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

A. J

What letter comes next in the series: z, x, v, t, ?

C. Q