题目

某企业购置了一批设备投入生产，据分析每台设备生产的总利 润（单位：万元）与年数满足如图的二次函数关系. 要使生产的年平均利润最大，则每台设备应使用___________年． 答案：5     The topics of a travel journal can be different from a diary, often _______ people, things, and events __________ the readers. A．including…less familiar withB．included…familiar toC．including…less familiar toD．including… less familiar than