A:H+、SO42﹣、OH﹣
B:H+、Cl﹣、CO32﹣
C:Cu2+、Cl﹣、OH﹣
D:Na+、NO3﹣、SO42﹣
①向上排空气法 ②向下排空气法 ③排水法.
人的口腔上皮细胞所处的内环境是
——I want to put up the picture on the wall. Would you mind helping me with it?—— ______. With pleasure.