In the sequence 2, 4, 8, ?, 32, 64, what is the missing number?

A. 16

In the series X, Y, Z, A, ?, C, D, what character should fill the gap?

A. B

SUN is to DAY as MOON is to ?

A. NIGHT

In the series X, Y, Z, ?, B, C, what character should fill the gap?

A. A

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

A. D