下列函数中，最小正周期为π的奇函数是(      )

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                                                                                                               春  兴
                                                                                                       （唐）武元衡
                                                                                   杨柳阴阴细雨晴，残花落尽见流莺。
                                                                                   春风一夜吹乡梦，又逐春风到洛城。

下列说法正确的是（   ）