Explanation:

Here is the breakdown of the options:

- Option 1: WRO

- W (23rd letter in the alphabet)

- R (18th letter)

- O (15th letter)

- The difference between successive letters: W to R (-5), R to O (-3)

- Option 2: HDA

- H (8th letter)

- D (4th letter)

- A (1st letter)

- Difference: H to D (-4), D to A (-3)

- Option 3: LHE

- L (12th letter)

- H (8th letter)

- E (5th letter)

- Difference: L to H (-4), H to E (-3)

- Option 4: PLI

- P (16th letter)

- L (12th letter)

- I (9th letter)

- Difference: P to L (-4), L to I (-3)

The clusters in Options 2, 3, and 4 follow a pattern with descending differences of -4, -3. While Option 1, WRO, has descending differences of -5, -3, making it the odd one out.

- Correct Answer: Option 1 - WRO