A series is given with one term missing. Choose the correct alternative from the given ones that will complete the series.
?, WX, AB, FG

Let's identify the gaps between consecutive clusters by observing the transitions of the letters:
Given pairs: ?, WX, AB, FG

Let's examine the distance between the first letters of known consecutive pairs:

From W to A: W
+4

​
A (since W(23)→X(24)→Y(25)→Z(26)→A(1))

From A to F: A(1)
+5

​
F(6)

Thus, the pattern for the gap between consecutive terms increases by 1 at each step (+3,+4,+5).
Let's reverse engineer from W with a difference of +3:

First letter of missing term+3=W(23)⟹23−3=20⟹T
Similarly, for the second letter:

From X(24) to B(2): X
+4

​
B

From B(2) to G(7): B
+5

​
G

So, tracking back from X with a difference of +3:

Second letter of missing term+3=X(24)⟹24−3=21⟹U
Thus, the missing term is TU.