Select the letter that will come next in the following series.
Z, X, U, Q, L, ?

Given: 

Z (26th letter) → X (24th letter): Difference of -2

X (24th letter) → U (21st letter): Difference of -3

U (21st letter) → Q (17th letter): Difference of -4

Q (17th letter) → L (12th letter): Difference of -5

Step 2: Determine the next letter

The difference between consecutive letters is increasing by 1 each time (-2, -3, -4, -5).

Following this pattern, the next difference will be -6.

Subtract 6 from the position of L (12th letter):

12−6=6, which corresponds to the letter F.

Final Answer: F