Complete the series:
XZB - UWY - RTV - ?

The correct option is OQS.

To find the missing term in the given series XZB - UWY - RTV - ?, let us analyze the pattern followed by the letters in each position of the triplets across the series.

Step 1: Analyze the first letter of each triplet
The first letters are: X, U, R, ...
Using alphabetical position numbers:
X = 24
U = 21 (24 - 3 = 21)
R = 18 (21 - 3 = 18)
Subtract 3 to find the next letter:
18 - 3 = 15
The 15th letter of the alphabet is O.

Step 2: Analyze the second letter of each triplet
The second letters are: Z, W, T, ...
Using alphabetical position numbers:
Z = 26
W = 23 (26 - 3 = 23)
T = 20 (23 - 3 = 20)
Subtract 3 to find the next letter:
20 - 3 = 17
The 17th letter of the alphabet is Q.

Step 3: Analyze the third letter of each triplet
The third letters are: B, Y, V, ...
Using alphabetical position numbers:
B = 2 (or 28 when wrapping around from Z)
Y = 25 (28 - 3 = 25)
V = 22 (25 - 3 = 22)
Subtract 3 to find the next letter:
22 - 3 = 19
The 19th letter of the alphabet is S.

Combining all three letters gives OQS.