In a certain code language, ‘ZCJV’ is coded as ‘YBIU’ and ‘GKMD’ is coded as ‘FJLC’. How will ‘EYOR’ be coded in that language?

Correct — B. Every letter steps back one place in the alphabet.

Rule: each letter − 1
ZCJV → YBIU, since Z−1 = Y, C−1 = B, J−1 = I, V−1 = U
GKMD → FJLC, since G−1 = F, K−1 = J, M−1 = L, D−1 = C

Apply it to EYOR: E−1 = D, Y−1 = X, O−1 = N, R−1 = Q.

That gives DXNQ — option (b).

Why the others are wrong

• (a)
  DWMP — D is right, but W, M and P are each two places back from Y, O and R. The step is one letter, and it has to be the same step everywhere.
• (c)
  CXNQ — The last three letters are right. The first is C, which is E − 2, so only the opening letter has been shifted twice.
• (d)
  QWMP — Q is what R becomes, not what E becomes, and W, M and P are two steps back rather than one. Nothing in this option is a single consistent shift.

A letter-code question is a substitution rule, and the first rule to test is always the simplest one: a constant shift.

Write the code under the plaintext and read the gaps. Z→Y, C→B, J→I and V→U are all −1, and the second example repeats it. Two examples agreeing on one constant settles the rule.

Only when a constant shift fails do you go looking for reversals, positional swaps or vowel-and-consonant rules.

Key facts

• The code is a uniform backward shift of one letter.
• Under that shift EYOR becomes DXNQ.
• Alphabet positions in play: E = 5, Y = 25, O = 15 and R = 18.
• A uniform shift preserves letter order, so a rearranged option is wrong on sight.

Common traps

• Shifting forward instead of backward, which turns EYOR into FZPS
• Applying a two-step shift after checking only one letter pair
• Forgetting the wrap-around, which bites as soon as a letter is A or Z

No directly related past PYQ was found.