Complete the series: a, e, i, o, ?

A. U

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

A. R

Identify the missing letter in the series: Z, X, V, T, ?

A. R

What number should replace the question mark in the series: 3, 6, 11, 18, ?, 38

B. 26

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

A. R