Using the same code ("P + Q": P is the father of Q; "P − Q": P is the sister of Q; "P × Q": P is the brother of Q), what does "X − Y × Z" mean?
Correct answer: C. X is the sister of Z.
"X − Y" means X is the sister of Y, and "Y × Z" means Y is the brother of Z. So X, Y and Z are siblings, and X, being a sister, is the sister of Z.
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