题目

20．下列各组物质中能在pH=1的溶液中大量共存，且得到无色透明溶液的是（   ） A.  BaCl2、NaNO3、KOH、MgCl2             B. Cu(NO3)2、NaCl、H2SO4、KNO3 C.  Na2CO3、NaCl、KNO3、NH4Cl            D.ZnSO4、Mg(NO3)2、NaNO3、KCl 答案：D(2012·安徽) In order to find the missing child, villagers __________ all they can over the past five hours.A. did B. doC. had done D. have been doing