Select the option that is related to the fifth letter-cluster in the same way as the second letter-cluster is related to the first letter-cluster and the fourth letter-cluster is related to the third letter-cluster.
MAILED : DELMAI :: FABRIC : CIRFAB :: JACKET : ?

The correct option is TEKJAC.

Let us analyze the pattern followed by the given letter-clusters:
Each 6-letter word is divided into two halves of 3 letters each (the first 3 letters and the last 3 letters).

First Pair: MAILED : DELMAI
1. First half: MAI
2. Second half: LED
3. Reversing the second half gives: LED ⇒ DEL
4. Combining the reversed second half with the original first half gives: DEL + MAI = DELMAI.

Second Pair: FABRIC : CIRFAB
1. First half: FAB
2. Second half: RIC
3. Reversing the second half gives: RIC ⇒ CIR
4. Combining the reversed second half with the original first half gives: CIR + FAB = CIRFAB.

Applying the same rule to JACKET:
1. First half: JAC
2. Second half: KET
3. Reversing the second half gives: KET ⇒ TEK
4. Combining the reversed second half with the original first half gives: TEK + JAC = TEKJAC.

Hence, the related letter-cluster for JACKET is TEKJAC.