Which of the following terms will replace the question mark (?) in the given series? XJUM, VLSO, TNQQ, RPOS, ?

Correct — D. Four-letter terms mean four separate one-letter series.

Rule: positions 1 and 3 fall by 2; positions 2 and 4 rise by 2.

1st: X → V → T → R → P (24, 22, 20, 18, 16)
2nd: J → L → N → P → R (10, 12, 14, 16, 18)
3rd: U → S → Q → O → M (21, 19, 17, 15, 13)
4th: M → O → Q → S → U (13, 15, 17, 19, 21)

Reading down the new column gives PRMU, option (d).

Why the others are wrong

• (a)
  PRMT — PRMT has the first three letters right and ends in T. The fourth series climbs M, O, Q, S, so it must reach U.
• (b)
  QRMT — QRMT starts at Q, one place short. The first series falls by 2 — X, V, T, R — and lands on P.
• (c)
  PRNU — PRNU puts N in the third slot. That series falls by 2 — U, S, Q, O — so the next letter is M, not N.

A four-letter series is four stacked one-letter series. Write the alphabet position under every letter of every term and four short arithmetic sequences appear.

Look for symmetry in the steps. Here two positions fall by 2 and two rise by 2, which is why the printed terms look scrambled while the arithmetic behind them is trivial.

Once the four steps are known, build the answer yourself and then find it among the options. That order is faster and immune to an option that matches on three letters out of four.

Key facts

• A = 1 and Z = 26, and letter pairs that sum to 27 (A-Z, B-Y, M-N) speed up position recall.
• The steps here are −2, +2, −2, +2 across positions 1 to 4.
• Four printed terms give three gaps — verify all three before extending.

Common traps

• Solving position 1 and assuming the other three share its step
• Dropping a step while counting through the middle of the alphabet
• Choosing an option that matches on three of the four letters

No directly related past PYQ was found.