Explanation:

- Notice the pattern in the series: ACF, DFI, GIL, JLO.

- Each set of letter-clusters increases by 3 positions forward in the alphabet:

- A ? D ? G ? J (first letters) ascend by +3.

- C ? F ? I ? L (second letters) also ascend by +3.

- F ? I ? L ? O (third letters) similarly ascend by +3.

- Therefore, all three letters in the clusters move forward by three places.

- Following this pattern:

- J (+3) ? M

- L (+3) ? O

- O (+3) ? R

- This leads to the letter-cluster "MOR" for the next sequence.

The correct answer is therefore Option 3: MOR.

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