In a certain code, PLANE is written as QMBOF. How is TRAIN written in that code?

Correct — A.
Rule: every letter moves +1.

PLANE → QMBOF: P→Q, L→M, A→B, N→O, E→F.

Apply it to TRAIN:
T→U, R→S, A→B, I→J, N→O
= USBJO → option (a).

Why the others are wrong

• (b)
  USQJO — USQJO has Q in the third place. TRAIN's third letter is A, and A + 1 is B, not Q.
• (c)
  USBOJ — USBOJ has the right letters with the last two swapped. The code shifts letters in place, so J (from I) must come before O (from N).
• (d)
  URBJO — URBJO leaves R unchanged in the second place. Every letter moves +1, so R must become S.

A letter-shift code moves every letter by the same amount. Find the shift from the given pair, check that it holds for every letter, then apply it to the new word in the same order.

Here P→Q, L→M, A→B, N→O and E→F are all +1. TRAIN therefore becomes USBJO, with each letter coded where it stands.

Key facts

• PLANE → QMBOF is a uniform +1 shift.
• A shift code keeps letter order: the first letter codes to the first letter, and so on.

Common traps

• Shifting most letters and copying one across unchanged, as in URBJO
• Coding the right letters but writing them in a different order, as in USBOJ

No directly related past PYQ was found.