题目

Listen and write down the sentences. 答案：【1】There was a time when the girl lost the power of speech.滴有紫色石蕊试液的氢氧化钠溶液慢慢地滴加稀盐酸至过量，溶液的（  ） A、颜色由红色变成蓝色；B、pH慢慢地降至7；C、颜色由蓝色变紫色；D、颜色由蓝色变红色