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

B. H

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

A. E

In the series X, Y, Z, ?, B, C, what character should fill the gap?

A. A

In the series: 1, 4, 9, ?, 25, what number should replace the question mark?

A. 16

In a pattern of letters: X, Y, Z, A, B, ?, D, E, what is the missing letter?

A. C