Identifying the Odd Letter Cluster Pair

The question asks to identify which pair of letter clusters does not follow the same logical pattern as the other three, based on the English alphabetical order.

Analyzing the Group Pattern

Three of the given options exhibit a consistent pattern involving letter positions in the alphabet. This pattern can be described as follows:

• First Cluster: Composed of two letters, say Letter1 and Letter2. The position of Letter2 is 4 places after Letter1 (P(Letter2) = P(Letter1) + 4).
• Second Cluster: Composed of two letters, say Letter3 and Letter4. The position of Letter4 is 4 places after Letter3 (P(Letter4) = P(Letter3) + 4).
• Inter-Cluster Relationship: The position of Letter3 is 3 places after Letter1 (P(Letter3) = P(Letter1) + 3). This implies P(Letter4) = P(Letter2) + 3 as well.
• Consecutive Check: Letter3 immediately precedes Letter2 in the alphabet (P(Letter3) = P(Letter2) - 1).

Evaluating Each Option

Option 1: AE-DH

Positions: A(1), E(5), D(4), H(8).

• Within AE: P(E) = P(A) + 4 (5 = 1 + 4).
• Within DH: P(H) = P(D) + 4 (8 = 4 + 4).
• Between clusters: P(D) = P(A) + 3 (4 = 1 + 3).
• Consecutive check: P(D) = P(E) - 1 (4 = 5 - 1).
• This pair fits the established pattern.

Option 3: FJ-IM

Positions: F(6), J(10), I(9), M(13).

• Within FJ: P(J) = P(F) + 4 (10 = 6 + 4).
• Within IM: P(M) = P(I) + 4 (13 = 9 + 4).
• Between clusters: P(I) = P(F) + 3 (9 = 6 + 3).
• Consecutive check: P(I) = P(J) - 1 (9 = 10 - 1).
• This pair fits the established pattern.

Option 4: CG-FJ

Positions: C(3), G(7), F(6), J(10).

• Within CG: P(G) = P(C) + 4 (7 = 3 + 4).
• Within FJ: P(J) = P(F) + 4 (10 = 6 + 4).
• Between clusters: P(F) = P(C) + 3 (6 = 3 + 3).
• Consecutive check: P(F) = P(G) - 1 (6 = 7 - 1).
• This pair fits the established pattern.

Option 2: NR-OU

Positions: N(14), R(18), O(15), U(21).

• Within NR: P(R) = P(N) + 4 (18 = 14 + 4). This part is consistent.
• Within OU: P(U) = P(O) + 6 (21 = 15 + 6). This violates the P(Letter4) = P(Letter3) + 4 rule.
• Between clusters: P(O) = P(N) + 1 (15 = 14 + 1). This violates the P(Letter3) = P(Letter1) + 3 rule.
• Consecutive check: P(O) = P(R) - 3 (15 = 18 - 3). This violates the P(Letter3) = P(Letter2) - 1 rule.
• Since multiple aspects of the pattern are broken, this option is the odd one out.

Final Determination

Option B (NR-OU) is the pair that does not conform to the specific alphabetical relationship pattern observed in the other three options.