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

Complete the series: A, C, E, G, ?

A. I

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

D. I

Find the missing letter in the series: z, x, v, t, ?

A. R