Complete the series: z, x, v, t, ?

A. R

What is the next letter in the series: m, o, q, s, ?

A. T

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

A. J

What letter comes next in the series: a, e, i, o, ?

A. U

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

A. S