Complete the series: 10, 20, 40, 80, ?, 320.

A. 160

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

A. J

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

C. Q

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

A. J

Complete the series: b, d, f, h, ?

D. I