题目

When I was a foreign teacher in China，every day I taught English to my students and they taught me about China．One day the topic mined to saying “I love you”．I was shocked to learn that not one of my students had said this to their mothers，nor had their mothers said it to them．“Does your mom love you?” “Of course，”they answered．     “How do you know?” was my logical question．They responded that their moms cooked and Always told them what they were doing wrong to show their earning．I was strummed. So mom's cooking and criticizing read our as “I love 6、含有硝酸锌、硝酸镁、硝酸铜、硝酸银四种溶质的溶液中加入一定量的铁粉，充分反应后过滤，滤纸上一定有 银，滤液中一定有 硝酸亚铁、硝酸镁、硝酸锌；如果滤纸上有铜，则滤纸上一定也有 银，滤液中一定有 硝酸亚铁、硝酸镁、硝酸锌，滤液中一定没有 硝酸银；如果滤纸上有铁，则滤纸上一定同时还有 银和铜，滤液中一定有 硝酸亚铁、硝酸镁、硝酸锌．