中考复习阶段，小荷同学梳理了以下知识：

①煮沸可以降低井水的硬度；

②向某固体上滴加稀盐酸，有气泡产生﹣﹣该固体一定是碳酸盐；

③用酒精浸泡捣烂的某些植物的花瓣可制得酸碱指示剂；

④“粗盐中难溶性杂质的去除”的实验中，当蒸发皿中出现较多固体时，停止加热；

⑤单质是由一种元素组成的物质，则由一种元素组成的物质一定是单质；

⑥有盐和水生成的反应一定是中和反应；

⑦自制简易净水器中的活性炭能吸附、过滤水中的杂质；

其中正确的是（　　）

阅读短文，下列问题

    Everybody wants to be healthy. You know food is very important.There are many healthy foods. You can have more bananas, apples, oranges,tomatoes and lettuce because fruits and vegetables are good for you. But don't eat too much chocolate. It's not good for you. But don't eat too much chocolate. It's not good healthy food. Healthy food can make you grow and make you strong and happy. Remember there is a saying, “An apple a day keeps the doctor away.” Sports can also keep you healthy. Get up early and do some sports every day. Don't be lazy! You will be healthy and happy.