What would be the next group of letters in the following series? SZ ... YR ... QX ... WP ... ?

To determine the next group of letters in the series SZ, YR, QX, WP, we need to examine the patterns present in the letters.

1. First Letters:
   • The first letters in each pair are S, Y, Q, W.

• The movement through the alphabet can be analyzed as follows:
  • S (19th letter), Y (25th letter): Move forward 6 letters
  • Y (25th letter), Q (17th letter): Move backward 8 letters
  • Q (17th letter), W (23rd letter): Move forward 6 letters

Following this pattern, the next movement would be backward 8 letters from W (23rd letter).

• Moving 8 letters back from W:
  • W (23) → V (22) → U (21) → T (20) → S (19) → R (18) → Q (17) → P (16) → O (15)
• The result is O as the first letter of the next pair.

2. Second Letters:
   • The second letters in each pair are Z, R, X, P.