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

A. 16

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

C. H

In the series X, Y, Z, A, ?, C, D, which letter should fill the gap?

A. B

In a pattern of shapes: Circle, Triangle, Square, Circle, Triangle, ?, Square. What is the missing shape?

B. TRIANGLE

Identify the missing character in the series: 2, 4, 6, ?, 10, 12.

B. 8