Explanation:

Let’s break this down step by step:

- Look at the pattern in each cluster:

acbd

fheg

ikjl

npmo

?

vxuw

- Each group is four letters. Let’s organize the letters by their position:

- 1st: a, f, i, n, ?, v

- 2nd: c, h, k, p, ?, x

- 3rd: b, e, j, m, ?, u

- 4th: d, g, l, o, ?, w

- The first letters: a (+5) f (+3) i (+5) n (+7) v

- a(1), f(6), i(9), n(14), v(22) — jumps of +5, +3, +5, +7.

- Let’s check the second position:

- c(3), h(8), k(11), p(16), x(24) — jumps of +5, +3, +5, +8.

- Third position:

- b(2), e(5), j(10), m(13), u(21) — jumps of +3, +5, +3, +8.

- Fourth position:

- d(4), g(7), l(12), o(15), w(23) — jumps of +3, +5, +3, +8.

- It’s alternating jumps between 5 and 3, then big jumps at the end.

- Options:

Option 1: prqs

Option 2: rtqs

Option 3: qsrt

Option 4: rtsu

- Fill the missing row: after n, the next set should start with:

n(+7)=u, p(+8)=x, m(+8)=u, o(+8)=w (but that matches vxuw, which is the last one!)

So before vxuw should be:

n (+5) = s, p (+5) = u, m (+5) = r, o (+5) = t ? surt, but no such option...

- Wait, cross-check: Maybe the series is moving alphabetically within pairs.

- ac bd, fh eg, ik jl, np mo, ? vx uw

- See: 'a-c', 'b-d', 'f-h', 'e-g' etc. — two pairs per cluster.

- Next after np, mo is... qs, rt.

- So option 3: qsrt sticks with the ongoing, logical pattern.

Answer: Option 3: qsrt