Explanation:

Let’s break it down step by step:

- There are four letters in each cluster. Let's track each position independently.

- 1st letter sequence: H, A, T, M, ?

- Look at the positions in the alphabet: H(8), A(1), T(20), M(13)

- Pattern: -7, +19, -7, so next: +19 ? 13 + 19 = 32, back to A(1), B(2),...Z(26), then 32-26 = 6 (F)

- 2nd letter sequence: I, C, W, Q, ?

- I(9), C(3), W(23), Q(17)

- Pattern: -6, +20, -6, next: +20 ? 17+20=37 ? 37-26=11 (K)

- 3rd letter sequence: R, Y, F, M, ?

- R(18), Y(25), F(6), M(13)

- Pattern: +7, -19, +7, next: -19 ? 13-19=-6, wrap forward: 26-6=20 (T)

- 4th letter sequence: C, I, O, U, ?

- C(3), I(9), O(15), U(21): +6 each time, next: 21+6=27; 27-26=1 (A)

- So the cluster is FKTA.

Option 3 matches: FKTA

The other options don't fit the pattern:

- 1 (HKTA): H is not correct for the first position

- 2 (GKTA): G is likewise a mismatch

- 4 (HKTZ): last letter is Z, it should be A based on pattern

Bottom line: Option 3 is the right answer and matches all parts of the logical sequence.