对于某些离子的检验及结论一定正确的是

A．向某溶液中滴加NaOH溶液并加热，用湿润的蓝色石蕊试纸置于试管口以检验NH₄^＋

B．加入氯化钡溶液有白色沉淀产生，再加入盐酸，沉淀不消失，一定有SO₄^2-

C．加入稀盐酸产生无色气体，将气体通入澄清石灰水中，溶液变浑浊，不一定有CO₃^2-

D．溶液中滴入酚酞试液若不变红，说明溶液一定是酸性溶液

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