WAEC 2022 · Paper 1 · Q18

Pick any one person: there are 5 people they can be paired with.

Of the 4 people left, pick one: they have 3 possible partners, and the last two form the final pair.

So there are $5 \times 3 \times 1 = 15$ ways, option C.

(Counting the possible pairs, $^{6}C_2 = 15$, gives the same number.)