Four letter-clusters have been given, out of which three are alike in some manner and one is different. Select the one that is different.

Let's analyze the differences between consecutive letters in each option:Option A: CIL
$$\text{C}(3)\stackrel{+6}{\to }\text{I}(9)\stackrel{+3}{\to }\text{L}(12)$$
Option B: GMR
$$\text{G}(7)\stackrel{+6}{\to }\text{M}(13)\stackrel{+5}{\to }\text{R}(18)$$
Option C: FLQ
$$\text{F}(6)\stackrel{+6}{\to }\text{L}(12)\stackrel{+5}{\to }\text{Q}(17)$$
Option D: TZE
$$\text{T}(20)\stackrel{+6}{\to }\text{Z}(26)\stackrel{+5}{\to }\text{E}(5\text{ or }31)$$
In options B, C, and D, the gap between the first and second letter is $+6$, and the gap between the second and third letter is $+5$.However, in Option A (CIL), the second gap is $+3$. Thus, CIL is the odd one out.