If 'ABCDE' is coded as 'EDCBA', 'FGHIJ' is coded as 'JIHGF', and 'KLMNO' is coded as 'ONMLK', then how is 'PQRST' coded?

Correct — A. Compare each word with its code.

Rule: the code is the word written backwards (ABCDE → EDCBA).

FGHIJ → JIHGF and KLMNO → ONMLK follow the same rule.

PQRST backwards: T, S, R, Q, P = TSRQP, option (a).

Why the others are wrong

• (b)
  TSRQQ — TSRQQ writes Q twice and drops P. A reversal uses every letter once, and the last letter must be P, the first letter of PQRST.
• (c)
  TSSQP — TSSQP writes S twice and drops R. In a five-letter reversal the middle letter stays in the middle, so the third letter must be R.
• (d)
  TSRRP — TSRRP writes R twice and drops Q. Q is second in PQRST, so it must be second from the end in the code.

A reversal code changes the order of the letters and nothing else. Two quick checks settle any option: the code must use exactly the letters of the word, each once, and the word's first letter must end the code.

In a five-letter word the middle letter keeps its place: C in ABCDE, H in FGHIJ, M in KLMNO, R in PQRST.

Key facts

• Written backwards, PQRST is TSRQP.
• A reversal keeps every letter exactly once.
• In a five-letter reversal the third letter does not move.

Common traps

• Checking the first letters and stopping, when every option begins TS.
• Looking for a letter shift because the given words run in alphabet blocks (ABCDE, FGHIJ), when the code only reverses them.

No directly related past PYQ was found.