What is the next letter in the series: A, C, E, G, ?

B. H

What letter should come next in the series: a, c, e, g, ?

B. H

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

A. J

What number should replace the question mark in the series: 3, 8, 15, 24, ?, 60

B. 36

Identify the missing letter: x, u, r, o, ?

A. L