题目[题目]-|||-设a为常数,则级数 sum _(n=1)^infty (dfrac (sin (nalpha ))({n)^2}-dfrac (1)(sqrt {n)}) 是 () ,-|||-(A)绝对收敛 (B)条件收敛-|||-(C)发散 (D)收敛性与α取值有关题目解答答案