题目

为确保信息安全，信息需加密传输，发送方由明文→密文（加密），接收方由密文→明文（解密）.已知加密规则为：明文a,b,c,d对应密文a+2b,2b+c,2c+3d，4d.例如，明文1,2,3,4对应密文5,7,18,16.当接收方收到密文14，9，23,28时，则解密得到的明文为（    ）A.7,6,1,4               B.6,4,1,7              C.4,6,1,7              D.1,6,4,7The term food "recovery" refers to the Collection, or recovery, of healthy food from farmers' fields, retail stores, or foodservice establishments for distribution to the poor and hungry. Food recovery programs operate across the United States and target many different levels of the food marketing system. A few are large operations with offices in many States, but most are small local programs that depend largely on the efforts of volunteers from the surrounding community. Once surplus food has been “recovered” or prevented from going to waste, volunteers pick up and deliver the food to groups that serve the needy, either directly through neighborhood charitable organizations, such as food chambers and soup kitchens, or indirectly through food banks. In addition to providing additional quantities of food to hungry people, food recovery  efforts can also provide food banks with the ability to offer clients more variety and nutrients (营养) in their diets by adding fiber-rich fresh fruits and vegetables and grain products to the typical offerings of indefectible canned and boxed goods. Food recovery also has benefits that extend beyond providing food to the needy. For example, the additional food supplied by recovery programs allows agencies that serve the disadvantaged to reallocate money to other needed services, money that they would have otherwise spent on food. These efforts also provide clean fields and tax savings for farmers who donate (捐赠) unharvested crops and reduce waste-removal fees for supermarkets and foodservice establishments. Food recovery, however, is not without cost. Recovery operations face a number of logistical (后勤的) and financial obstacles in the course of turning "lost" food into food suitable for consumption. At times, these obstacles are quite powerful. They include locating food donors and making them aware of organizations that channel donated food to the needy; obtaining financial  resources for transporting, storing, and packaging donated foods; securing labor, whether paid or volunteer; and training those workers in safe food handling and preparation methods. 　　 1. Food recovery programs mainly aim at——. 　　　　 A. collecting money from donors to deal with the food waste problem 　　　　 B. collecting money from donors to provide food to the needy 　　　　 C. collecting money and healthy food to provide food to the needy 　　　　 D. collecting money and healthy food for charitable organizations 　　 2. In addition to providing food to the needy, food recovery programs also——. 　　      A. distribute money directly to the needy 　　　　  B. help farmers improve their productivity 　　　　  C. are involved in other charitable services 　　　　  D. help some agencies reduce food waste 　　 3. Which of the following is NOT the cost of food recovery mentioned in the passage? 　　　　  A. Publication for food recovery courses. 　　　　  B. Collecting money for recovery courses. 　　　　  C. Enrolling volunteers for recovery courses. 　　　　  D. Encountering some obstacles from the government. 　　 4. According to the passage, which of the following is NOT true? 　　　　  A. Food recovery programs are mainly involved in charitable services. 　　　　  B. Food recovery programs are involved in promoting nutritional balance. 　　　　  C. All staff of Food recovery programs are volunteers without pay. 　　　　  D. Many supermarkets and farmers are involved in Food recovery programs.