In the pattern: X, Y, Z, ?, B, what character is missing?

A. A

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

A. D

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

A. 16

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

A. Z