Find the Next Pair: AZ, CX, FU, (?) — determine the next two-letter code using consistent forward/backward jumps.

Introduction / Context:
Two-letter codes frequently move forward on the first letter and backward on the second, with step sizes themselves increasing in a simple progression.

Given Data / Assumptions:

• Pairs: AZ, CX, FU, ?
• First letters: A → C → F → ? (forward)
• Second letters: Z → X → U → ? (backward)

Concept / Approach:
Identify the step pattern: first letters go +2, then +3, then +4; second letters go −2, then −3, then −4.

Step-by-Step Solution:
First letter: A(+2)=C, C(+3)=F, F(+4)=J → next first letter J.Second letter: Z(−2)=X, X(−3)=U, U(−4)=Q → next second letter Q.Hence the next pair is JQ.

Verification / Alternative check:
Both directions’ step sizes increase by 1 each time, so JQ is uniquely determined.

Why Other Options Are Wrong:

• IR, IV, KP: they violate the +2/+3/+4 and −2/−3/−4 stepping scheme.

Common Pitfalls:
Keeping step sizes constant rather than increasing them by 1 at each move.

Final Answer:
JQ