第21题: [单项选择]They have been waiting for many hours. The airplane must have been______. A. of schedule B. on schedule C. ahead of schedule D. behind schedule 参考答案:D 答案解析:本题测试介词短语的用法。根据题意,是指航班晚点,故应选behind schedule“落后于预定计划”。of schedule搭配不存在;on schedule“按时”;ahead of schedu
第34题: [填空题]Most of the foods grown and processed according to the federal standards will bear the seal ______. 参考答案:"USDA Organic" 答案解析:[解析] 本题和标识有关。根据小标题How Do I Know if a Food is Organic 部分第二段第一句Foods grown and processed according to