Based on the English alphabetical order, three of the following four letter-clusters are alike in a certain way and thus form a group. Which letter-cluster does not belong to that group?
(Note: The odd letter-cluster is not based on the number of consonants/vowels or their position in the letter-cluster.)

The correct option is JQM.

Step-by-step Explanation:

Let us analyze the position of each letter in the English alphabetical order (where A = 1, B = 2, ..., Z = 26) to find the pattern linking the letters within each cluster.

1. OVS:
O = 15, V = 22, S = 19
Pattern: 15 + 7 = 22 (V), and 22 - 3 = 19 (S)
OVS follows the pattern of (+7, -3).

2. LSP:
L = 12, S = 19, P = 16
Pattern: 12 + 7 = 19 (S), and 19 - 3 = 16 (P)
LSP follows the pattern of (+7, -3).

3. NUR:
N = 14, U = 21, R = 18
Pattern: 14 + 7 = 21 (U), and 21 - 3 = 18 (R)
NUR follows the pattern of (+7, -3).

4. JQM:
J = 10, Q = 17, M = 13
Pattern: 10 + 7 = 17 (Q), but 17 - 4 = 13 (M)
Here, the difference between the second and third letter is -4 instead of -3. Therefore, JQM does not follow the (+7, -3) pattern followed by the other three clusters.

Hence, JQM is the letter-cluster that does not belong to the group.