Select the letter-cluster that will replace the question mark:
ABB, BCC, CDD, ?

Question

Accepted Answer

1. Look at the groups: ABB, BCC, CDD.
2. The first letter moves one step each time: $A	o B	o C	o D$.
3. The second letter is the first letter plus one, and the third letter repeats the second.
4. For first letter $D$, second and third are $E$, so the group is **DEE**.

FINAL_ANSWER: <a>

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