Which of the following alternative will fill the blanks? pq_st_qr_tp_rst

Correct — A.
Rule: the block pqrst repeats.

Split the 15 places into fives: pq_st | _qr_t | p_rst.
Block 1: pqrst, so blank 1 = r
Block 2: pqrst, so blanks 2 and 3 = p, s
Block 3: pqrst, so blank 4 = q

Reading r, p, s, q → option (a).

Why the others are wrong

• (b)
  p,s,q,r — p in the first blank gives pqpst, which breaks the block at once: after pq the series needs r.
• (c)
  p,q,s,r — It also puts p in the first blank, so pq_st becomes pqpst instead of pqrst. The option fails before its later letters matter.
• (d)
  r,p,q,s — The first two blanks, r and p, are right. The third gives pqrqt where the block needs s, and the fourth gives psrst.

A blank-filling letter series hides a repeating block. Find its length first: 15 places and five different letters, p to t, suggest a five-letter block, 15 ÷ 5 = 3 copies.

Then line the string up in blocks and read each blank from its place inside the block. That is faster and safer than testing four options letter by letter.

Key facts

• 15 places with five different letters points to a five-letter block repeated three times.
• The completed series is pqrst pqrst pqrst.
• Each blank is fixed by its place in the block: 3rd, 1st, 4th and 2nd here.

Common traps

• Testing options without finding the block, and accepting r, p, q, s because its first two letters fit
• Splitting the string at the wrong place so the blocks do not line up

No directly related past PYQ was found.