Sam really felt very happy. When he arrived at his seat in the classroom that morning, he found an invitation on his desk. It was from several of his classmates asking him to join them on a camping trip. This was the first time he was asked to join in an out-of-school activity. Why were they asking him now? Nobody seemed to like him. In fact, he had been so lonely that he ate a lot of food. As a result, he put on a lot of weight, and this gave the kids something more to make fun of him. Cindy, who was standing near Sam when Sam read the invitation, went out quickly to tell the others that _ . Everyone was pleased that Sam thought that was true, but there was no camping trip. The whole thing was made up . At first, Cindy thought it was fun. But later, when Sam told her that he was going to buy a sleeping bag with his savings, Cindy had second thoughts. She knew that Sam's family had little money, and she hated to see him spend his savings  on something he would never use, Cindy also hated to tell Sam the truth. Her close friends would be angry with her. What can she do now? What do the words "the trick had worked" probably mean?
Sam had believed it. Cindy had helped Sam. Cindy had told Sam about the truth. Sam had bought something for the trip.