根据语篇内容，判断下列句子正误

A farmer was put in prison(监狱). One day, he got a letter from his wife. "I am worried about our farm, "she wrote. "It's time to plant potatoes , but I can't do all the digging(挖) by myself. " The farmer thought over and then had an idea. He wrote to his wife, "Don't dig the fields. This is where my gold(金子) is. Don't plant potatoes until I come home. " A few days later, the farmer got anther letter from his wife. It said, "Two days ago, about ten prison guards(监狱看守) came to our fields. It looked as if they were looking for something. They have dug our field. " The farmer wrote to his wife at once. "Now you can plant our potatoes, "he wrote.