第4题: [单项选择]Questions 16 to 18 are based on the passage you have just heard. A. They breathe fresh air. B. They don’t have diseases common in cities. C. They are in close touch with nature. D. They eat a lot of fresh vegetable. 参考答案:C 答案解析:[解析] Q: Why do country people enjoy good health
第30题: [单项选择]各种范式之间有一定关系,下面是( )正确的。 A. 4NF含于BCNF含于3NF B. 3NF含于BCNF含于4NF C. 5NF含于BCNF含于4NF D. 4NF含于BCNF含于5NF 参考答案:A 答案解析:[解析] 按照级别从高到低,各级范式之间的关系如下: 5NF[*]4NF[*]BCNF[*]3NF[*]2NF[*]1NF