Find the missing character in the series: X, W, V, ?, T.

A. U

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

A. D

In the sequence: A1, B2, C3, ?, E5, what is the missing term?

A. D4

In the series X, Y, ?, Z, what character is missing?

A. W

Bird is to Nest as Fish is to ?

B. AQUARIUM