[单项选择]Pneumonia is closely related to ______. A. the decline in ceils of the spinal chord B. the slower rote of reaction C. the decline in the immune system D. the loss of cells in kidneys
参考答案:C 答案解析:第二段谈到More subtle are such declines as those in the processes involved with be ing immune to disease，
第24题: [单项选择]公共物品供应的最优均衡条件为( )。 A. 每一个消费者的边际替代率必须相等 B. 生产者的边际成本应等于消费者的边际支出 C. 提供公共物品的私人成本等于提供公共物品的社会成本 D. 消费者的边际支付意愿之和应等于提供该公共物品的边际成本 参考答案:D 答案解析:[解析] 公共物品供应的最优均衡条件为消费者的边际意愿支付之和应等于提供该公共物品的边际成本。
