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

A. D

If the pattern is 1, 2, 4, ?, 16, what number should replace the question mark?

A. 8

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

A. Z

What character should replace the question mark in the sequence 3, 6, 9, ?, 15?

B. 12

In the pattern P, Q, R, ?, T, U, which character is missing?

A. S