Select the letter that can replace the question mark (?) in the following series.
O, B, L, C, I, D, F, E, ?
The series consists two series,
O, L, I, F, ?
And
B, C, D, E
O - 3Â = L
L - 3 = I
I - 3 = F
F - 3 = C
$$\therefore$$ The correct answer is option B.
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