第23题: [单项选择]在关系模型中,若属性A是关系R的主码,则在R的任何元组中,属性A的取值都不允许为空,这种约束称为( )规则。 A. 实体完整性 B. 参照完整性 C. 用户自定义完整性 D. 全部 参考答案:A 答案解析:[解析] 现实世界中的实体是可区分的,相应的,关系中的元组也是可区分的。实体完整性要求主属性不能为空值。如果主属性取空值,则意味着关系中的某个元组是不可标识的,即存在不可区分的实体,这与实体的定义矛盾
第25题: [单项选择]A client has had a cerebrovascular accident (CVA). Because the CVA affected the left side of the client’s brain, the nurse should anticipate that the client would most likely experience A. dyslexia. B. apraxia. C. agnosia. D. expressive aphasi 参考答案:D 答案解析:Broca’s area, which controls expressive speech, is located on the left side of the brain. Therefore,