某溶液中含有较大量的Cl-、CO、OH-等3种阴离子,如果只取一次该溶液能够分别将3种阴离子依次检验出来,下列实验操作顺序正确的是 ( ) ①滴加过量的Mg(NO3)2溶液 ②过滤 ③滴加AgNO3溶液 ④滴加(过量)Ba(NO3)2溶液 A.①②④②③ B.④②①②③ C.①②③②④ D.④②③②① 答案:B19.-We'll have a hiking trip,but when shall we meet?-Let's make it half past eight the morning of June 21.( )A.at; inB./; onC./; in