In a certain code language, 'OASIS' is written as 'RJTBN' and 'OBESE' is written as 'DTFCN'. How will 'OCCUR’ be written in that language?

Correct — D. No single shift fits, because S becomes T in one place and R in another. The shift depends on position, and the word is then written backwards.

Rule: positions 1 and 5 shift −1, positions 2, 3 and 4 shift +1; then reverse.

OASIS → N B T J R → reversed = RJTBN
OBESE → N C F T D → reversed = DTFCN

OCCUR: O−1 = N, C+1 = D, C+1 = D, U+1 = V, R−1 = Q, giving NDDVQ.

Reversed, that is QVDDN — option (d).

Why the others are wrong

• (a)
  QVNDD — QVNDD opens correctly but then puts the N third. Reversing NDDVQ sends N, the coded first letter, all the way to the end of the string.
• (b)
  VQDDN — VQDDN has the leading pair swapped. Reversing NDDVQ puts Q first and V second, because Q is the coded last letter.
• (c)
  VQNDD — VQNDD makes both errors together: the leading V and Q are the wrong way round and the N sits third instead of last.

Two clues tell you a code ends in a reversal.

First, a repeated letter takes two different codes — S is T once and R once in OASIS, which no uniform shift can do. Second, both given words begin with O and both codes end with N, and N is O − 1.

Once the reversal is suspected, write the code backwards and line it up letter for letter against the word. The shift table then falls out immediately, and here it is symmetric: the two outer letters go back one, the three inner letters go forward one.

Key facts

• In OASIS to RJTBN the letters map O to N, A to B, S to T, I to J, S to R.
• The shift by position is −1, +1, +1, +1, −1, and the result is then written backwards.
• Both given words start with O and both codes end with N, since O − 1 = N is pushed to the end by the reversal.

Common traps

• Hunting for one shift that covers the whole word, when S becomes both T and R.
• Applying the shifts and forgetting to reverse, which produces NDDVQ — not on the option list, so the error costs a full re-solve.
• Assuming the code's first letter answers to the word's first letter, when the reversal puts them at opposite ends.

No directly related past PYQ was found.