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

A. 16

In the series X, Y, Z, ?, B, C, which letter is missing?

A. A

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

A. D

In the pattern 2, 4, 6, ?, 10, 12, which number is missing?

B. 8

Identify the missing character in the series 1, 4, 9, ?, 25.

A. 16