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【单选题】
对函数f（x）=xsinx，现有下列命题： ①函数f（x）是偶函数； ②函数f（x）的最周期是2π； ③点（π，0）是函数f（x）的图象的一个对称中心； ④函数f（x）在区间 上单调递增，在区间 上单调递减．其中是真命题的是 [ ]A.
①④
B.
②④
C.
②③
D.
①③
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