In a sequence of letters: A, C, E, G, ?, K. What is the missing letter?

B. H

In the series: 1, 4, 9, 16, ?, 36. What is the missing number?

B. 25

In a pattern of letters: X, Y, ?, Z, A. What is the missing letter?

A. W

If the pattern is 1, 4, 9, ?, 25, 36, what number should replace the question mark?

A. 16

In the sequence A, B, C, ?, E, F, what character should replace the question mark?

A. D