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

A. D

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

A. P

What character should replace the question mark in the sequence: A, B, C, ?, E?

A. D

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

A. 16

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

A. E