题目

某学生将电流计用导线与两个电极相连，再将两个电极分别插入某种电解质溶液中，能观察到有电流产生的是（    ）A.用铜片、铅笔芯作电极插入稀硫酸中B.用两个铜片作电极插入硝酸银溶液中 C.用锌片、铜片作电极插入番茄中D.用铜片、铁片作电极插入酒精中 答案：解析：要构成原电池，除要构成闭合回路外，还需要有两个活泼性不同的电极，其中一个电极要能与电解质溶液发生氧化还原反应。A选项，铜与石墨与稀硫酸均不反应，B选项两个电极材料相同，D选项中酒精是非电解质，C选项中一些水果中含有有机酸可作电解质。答案：CCharles, a British teacher, also comes to visit Beijing Sunshine Secondary School with the exchange students. He wants to ask Mr Wu something about the school. Now he is making a list of questions. Help him complete the questions with'How much'and'How many'. ________________money does a student pay each year?