[Q]: Sentence: Imbalances between North and South were expressed in Nigeria's political life as well. Question: When did northern Nigeria ban slavery?
++++++++++
[A]: no

[Q]: Sentence: Occasionally he played, or accompanied the singing of Delfina Potocka, for his friends. Question: Who did Chopin play for while she sang?
++++++++++
[A]: yes

[Q]: Sentence: The legality of this action was questionable, since Soviet law did not allow a republic to unilaterally recall its deputies. Question: Who ratified the Accords?
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[A]:
no