These letter puzzles hide a fixed positional rearrangement. The trick is to label the four letters of the first word by their slots (1st, 2nd, 3rd, 4th) and then track where each slot travels in the second and third words. Whatever movement works for both sample triads must also work for the correct answer.

Take the first sample: BARS → ARBS → SRAB. Writing BARS as slots 1-2-3-4 = B-A-R-S:

• Second word ARBS = A, R, B, S. The first three letters rotate one place to the left (B moves behind A and R), while the last letter S stays put. So the rule is: first three letters shift left by one, fourth letter fixed.
• Third word SRAB is simply the complete reverse of BARS (S-R-A-B).

The second sample confirms it exactly: FLAM → LAFM → MALF. Here LAFM is F-L-A-M with the first three rotated left (L, A, F) and M fixed, and MALF is FLAM read backwards.

Now test the choice KEAT − EAKT − TAEK. Starting from KEAT: rotating the first three letters left gives E-A-K, keeping T fixed → EAKT ✓. Reversing KEAT gives T-A-E-K → TAEK ✓. Both steps match perfectly, so this is correct.

The other groups break down: in the set beginning BALK, the left-rotation of the first three letters should give ALBK, but the listed second word is ABLK, so the rule fails at the very first step. The set beginning MIND passes the first step (INMD is correct) but its third word should be the full reverse DNIM, whereas INDM is given — so the reversal rule is violated. In the set beginning WAST, the rotated second word should read ASWT, not the given WSAT. Hence KEAT − EAKT − TAEK is the only fully consistent triad.