Explanation:

Let's break down the pattern in the given letter-cluster series:

- SWA

- S ? C ? M ? ? (First letters)

- S(19), C(3), M(13): Pattern is -16, +10

- W ? G ? Q ? ? (Second letters)

- W(23), G(7), Q(17): Pattern is -16, +10

- A ? K ? U ? ? (Third letters)

- A(1), K(11), U(21): Pattern is +10, +10

But all transitions are not matching the same rule.

Let’s try to find a consistent pattern:

- First: S (19), C (3), M (13)

- S ? C = -16 (clockwise)

- C ? M = +10 (clockwise)

- Second: W (23), G (7), Q (17)

- W ? G = -16 (clockwise, 23 to 7)

- G ? Q = +10 (7 to 17)

- Third: A (1), K (11), U (21)

- A ? K = +10 (1 to 11)

- K ? U = +10 (11 to 21)

Now, predict the next:

- First: M (13) +10 = 23 ? 23 = W

- Second: Q (17) +10 = 27 Mod 26 = 1 ? 1 = A

- Third: U (21) +10 = 31 Mod 26 = 5 ? 5 = E

So, the missing term is WAE.

- Option 4: WAE

Summary of options:

- Option 1: XAE – incorrect, first letter wrong.

- Option 2: WZC – incorrect, 2nd and 3rd letters wrong.

- Option 3: VZD – incorrect, all letters off.

- Option 4: WAE – correct, fits the +10 pattern.

Correct Answer:

- Option 4: WAE