Explanation:

Alright, let’s break down how this code works:

- Look at GLADIATOR ? TROLIGDAA. The last four letters of “GLADIATOR” (“ATOR”) become the first four letters of the code.

- After that, the remaining letters (“GLADI”) are reversed (“IDALG”) and put at the end. But wait, in the code we see “IGDAA.” Let's check carefully:

- “G L A D I A T O R”

- Take the last four: T O R (But in the code it’s T R O L)

- It looks like the code scrambles the order: last four letters followed by reversed rest, but the rest is reversed and slightly rearranged.

- Taking another angle: Compare each segment:

- GLADIATOR: G L A D I A T O R

- TROLIGDAA: T R O L I G D A A

- Actually, see that the code splits into two parts: last four letters, then reverse of the first five.

- Last four: “ATOR” becomes “T R O L” (but out of order).

- First five: “GLADI” reversed is “IDALG”.

But in the code we get “TROL IGDAA”. Let's check: TROLIGDAA.

On closer inspection:

- Last letter to first: R

- Second last letter to second: O

- Third last to third: T

- Fourth last to fourth: A

- Then, the rest letters “GLADIA” get reversed: A I D A L G

- Wait, in code: TROLIGDAA

- T R O L : This is last four letters of word, reversed.

- Original: GLADIATOR

- Last four: A T O R. But here we have T R O L.

- Rearrangement: Take last four letters, move to front, reverse their order, then add the rest reversed.

- But the match doesn’t fully add up with a clear, single pattern.

Let's analyze by options for SKILLFUL:

- S K I L L F U L

- Last four letters: F U L L

- First four: S K I L

- The possible scheme: reverse last four, put at front, then reverse the rest.

Option check:

1. ULLFILSK — “ULLF” (reverse of “FULL”), then “ILSK” (reverse of “SKIL”). This matches the GLADIATOR scheme properly. So Option 1 fits.

2. LUFLLIKS — letters are not matching any clear reversal logic.

3. USLLLKIF — doesn't fit the pattern, out of order.

4. FIKLLLSU — similar, but not matching the split/reversal.

So here’s what’s really happening:

- Last four letters are reversed and put up front, then the remaining letters are reversed and added.

- For “SKILLFUL”: FULL (reversed: L L U F) + SKIL (reversed: L I K S) ? LLUFLIKS

But wait, none of the options are "LLUFLIKS", but option 1 is ULLFILSK which closely matches the exact reversal (reversal of FULL is LLUF, reversal of SKIL is LIKS).

But exactly, Option 1 is the one that most closely matches the pattern, but with a slight letter order difference from “GLADIATOR” example; let's read both codes side by side and see how the letters mapped.

After going over, Option 1: ULLFILSK matches the pattern best.

So:

- Option 1: ULLFILSK – This matches reversing the last four, then the rest.

- Option 2: LUFLLIKS – letters jumbled, not matching.

- Option 3: USLLLKIF – wrong order.

- Option 4: FIKLLLSU – no match.

Correct answer is Option 1: ULLFILSK

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