Find the group of letters that best completes the analogy based on the given letter transformation pattern. PAPER : QBUFS :: STONE : ?

Correct — C.
Rule: +1, +1, +5, +1, +1, letter by letter.

PAPER → QBUFS: P→Q, A→B, E→F and R→S are each +1.
The third letter breaks step: P(16) → U(21) is +5.

STONE: S→T, T→U, N→O and E→F (+1 each).
Third letter: O(15) + 5 = T(20).

That gives TUTOF → option (c).

Why the others are wrong

• (a)
  UTONI — UTONI starts with U, but S + 1 is T. Its middle letters T, O, N are copied unchanged from STONE, where the pattern moves every letter.
• (b)
  QVHRJ — QVHRJ starts with Q, two letters back from S. The pattern moves every letter forward, so the first letter must be T.
• (d)
  IPFHR — IPFHR starts with I, nowhere near S + 1 = T. Not one of its five letters matches the +1, +1, +5, +1, +1 result.

A letter-transformation analogy applies a fixed step to each position. Work the step out position by position from the given pair; do not assume every letter moves by the same amount.

Here four letters move +1 and the third moves +5. A uniform +1 would turn STONE into TUPOF, which is not offered, so the odd step is exactly where a careless reading fails.

Key facts

• Find the step for each position separately: here +1, +1, +5, +1, +1.
• O = 15 and T = 20, so O + 5 = T.
• A uniform +1 shift would give TUPOF, which is not among the options.

Common traps

• Assuming every letter moves +1 because four of five do, and looking for TUPOF
• Miscounting S + 1 and choosing UTONI

No directly related past PYQ was found.