(A ∩ B)' is the complement of A ∩ B, or the set of all elements in the universal set U that do not belong to A ∩ B.
A ∩ B is the intersection of A and B, or the set of all elements common to both A and B.
We have
A = {q, s, u, w, y}
B = {q, s, y, z}
so that
A ∩ B = {q, s, y}
Then
(A ∩ B)' = {r, t, u, v, w, x, z}
which makes (c) the answer.
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