Explanation:

Let's break down the logic in each pair:

- I4D : G9F

- I to G: Move 2 letters back.

- 4 to 9: 4×2+1 = 9.

- D to F: Move 2 letters forward.

- L16S : J25U

- L to J: 2 letters back.

- 16 to 25: 16×1.5+1 = 25 (or just +9, both not matching perfectly, but let's focus elsewhere).

- S to U: 2 letters forward.

- W64R : ?

- W to ?: 2 letters back ? U.

- 64 to ?: Either 64+17 or 8 squared + 17 = 81.

- R to ?: 2 letters forward ? T.

Given options:

1. U81T

2. S49T

3. U49T

4. T81U

- Only Option 1 matches all the logic (W to U, 64 to 81, R to T).

So, the correct answer is:

- ?? U81T (Option 1)

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