If "EUROPE" is coded as "AQNKLA", how is "RUSSIA" coded?

Correct — D.
Rule: every letter moves 4 places back (−4).

EUROPE: E → A, U → Q, R → N, O → K, P → L, E → A.

RUSSIA: R → N, U → Q, S → O, S → O, I → E.
A → W: counting back four from A gives Z, Y, X, W.

RUSSIA → NQOOEW → option (d).

Why the others are wrong

• (a)
  NOWOEU — NOWOEU goes wrong at the second letter: U − 4 is Q, not O. Its last letter U also misses the wrap, since A − 4 is W.
• (b)
  NUUMHX — NUUMHX leaves U unchanged in second place, where −4 gives Q. Its later letters move by different amounts, so no fixed step produces it.
• (c)
  OVTTEV — OVTTEV is wrong from the first letter: R − 4 is N, not O. It also moves S forward to T, the opposite direction to the code.

In a fixed-step code, every letter moves the same number of places. Read the step off one letter pair, confirm it on the rest, then apply it.

E (5) → A (1) is −4, and every EUROPE pair agrees. Take care at the wrap-around: moving back from A continues at Z, so A − 4 = W. RUSSIA ends in A, which is exactly where the wrap matters.

Key facts

• E → A, U → Q, R → N, O → K and P → L are all moves of −4.
• Moving back past A wraps to Z: A − 4 = W.
• Under −4, RUSSIA becomes NQOOEW.

Common traps

• Stopping the count at A instead of wrapping round to W
• Moving forward by 4 instead of back, which turns R into V

No directly related past PYQ was found.