There are two alphabetical series here.

The first series is with the first letters only: STUVW.

The second series involves the remaining letters: CD, EF, GH, IJ, KL.

Because the letters are the same, concentrate on the number series, which is a simple 2, 3, 4, 5, 6 series, and follows each letter in order.

The middle letters are static, so concentrate on the first and third letters.

The series involves an alphabetical order with a reversal of the letters.

The first letters are in alphabetical order: F, G, H, I , J.

The second and fourth segments are reversals of the first and third segments.

The missing segment begins with a new letter.

The second and forth letters in the series, L and A, are static.

The first and third letters consist of an alphabetical order beginning with the letter E.

The first letters are in alphabetical order with a letter skipped in between each segment: C, E, G, I, K.

The second and third letters are repeated; they are also in order with a skipped letter: M, O, Q, S, U.