In a series of numbers: 2, 4, 8, 16, ?, 64. What is the missing number?

B. 32

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

A. C

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

B. H

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

A. 16

In the series X, Y, ?, A, B, C, which character is missing?

A. Z