In a pattern of letters: X, Y, Z, A, B, ?, D, E, what is the missing letter?

A. C

What character should be inserted in the following pattern: 2, 4, 8, ?, 32?

A. 16

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