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

A. Z

What character should replace the question mark in the pattern X, Y, Z, A, B, ?

A. C

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

A. E

Find the missing letter in the series: M, N, O, ?, Q, R.

A. P

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

A. 16