In a certain code language, ‘CLERK’ is written as ‘BKEQJ’ and ‘OFFICE’ is written as ‘OEEIBE’. How will ‘POST’ be written in that language?

Correct — B. Rule: every consonant moves back one letter, every vowel stays put.

CLERK: C-1=B, L-1=K, E stays, R-1=Q, K-1=J, giving BKEQJ.
OFFICE: O stays, F-1=E, F-1=E, I stays, C-1=B, E stays, giving OEEIBE.

POST has one vowel. P-1=O, O stays O, S-1=R, T-1=S.

That is OORS -> option (b).

Why the others are wrong

• (a)
  RSOO — RSOO reorders the cluster before shifting. This code touches each letter where it stands and never moves a letter to a new position.
• (c)
  OROS — Position 2 of POST is the vowel O, which the rule leaves alone. OROS puts R there, so the shifted S has landed in the wrong slot.
• (d)
  OSOR — OSOR ends in R, but the final T must fall back one place to S. It also puts S at position 2, where the untouched vowel O belongs.

Two worked examples fix a code only if you test one idea against both of them.

The shifts here are not uniform. In CLERK four letters drop one place and E does not move, and in OFFICE the vowels O, I and E all sit still while F, F and C drop one.

The dividing line is vowel against consonant, not position. Once you see it, the target word is four independent one-letter decisions.

Key facts

• In this code every consonant moves one place back and every vowel is left unchanged.
• CLERK becomes BKEQJ because E is its only vowel.
• POST contains one vowel, so only P, S and T move, giving OORS.

Common traps

• Applying a uniform minus-one and shifting the vowel with everything else
• Reordering the letters, which no step of this code does
• Fixing the rule from one example word and never checking the second

No directly related past PYQ was found.