Explanation:

- Let's look at the letter series: C, W, E, U, ?

- Notice the pattern by looking at the positions of the letters in the alphabet.

- C (3rd) is followed by W (23rd), and the difference is -20.

- W (23rd) is followed by E (5th), and the difference is -18.

- E (5th) is followed by U (21st), and the difference is -16.

- The pattern shows the differences between positions shrink by 2 each time.

- Next, U (21st) to the unknown letter should have a difference of -14.

- 21 - 14 = 7, which corresponds to the letter G.

Therefore, Option 1: G is the correct choice.

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