Explanation:

- The series to be completed is: TSXA, XBLT, ?, FTNF, JCBY.

- Look for patterns in the sequences of letters.

- Observe the first letter of each cluster: T (+4) = X, X (+4) = B, B (+4) = F, F (+4) = J. This pattern shows each first letter moves forward by four in the alphabet.

- Check the second letter pattern: S (+2) = B, B (+2) = D (but D should correspond to the missing series), D (+2) = N, N (+2) = C.

- Examine the third letter: X (-3) = L, L (-3) = I, but should be I for the missing one, I (-3) = F, F (-3) = B.

- Look at the fourth letters to find a pattern: A (+19) = T, T (+19) =M, but should be M for the missing one, M (+19) = F, F (+19) = Y.

- Based on the deduction, the missing cluster is DJIM, not BKZM.

Option 4: BKZM is incorrect.

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