对地球圈层的主要特点，描述正确的是（  ）

下列各组词语中，没有错别字的一组是(　　)

①酸碱中和反应生成盐和水，所以生成盐和水的反应一定是中和反应：②氯化钠的水溶液显中性，所以盐溶液一定显中性；③分子可以构成物质，物质一定是由分子构成的；④碳酸盐与盐酸反应放出气体，所以与盐酸反应放出气体的一定是碳酸盐．

根据材料内容，选择正确答案。

    Jim, a young farmer, was once put into prison (监狱).

    One day, he got a letter from his mother. "I'm so worried about our farm," she wrote. "It's time to plant potatoes. I can't dig(挖) all the fields by myself. "

    Jim read the letter and became sad. "What can I do?" he thought. Then he had a good idea. He wrote to his mother, "Don't dig the fields. There's a pot of money in the earth. Don't plant potatoes until I come home."

    Some days later, Jim got another letter from his mother. It said, "Two days ago, about ten men came to our farm and dug all our fields. I can't understand it. It looks as if they were looking for something. What shall I do?"

    Jim smiled when he read his mother's letter. He wrote a letter to his mother at once. It was very short. Guess what it would say?