第3题: [单项选择]Which of the following is true of an index used to support a UNIQUE constraint?() A. It must have the UNIQUE attribute. B. It cannot be created explicitly by the user. C. It must have the UNIQUE and CLUSTER attributes. D. It must have the UNIQUE WHERE NOT NULL attribute. 参考答案:A
第32题: [单项选择]______ that the earth was flat A. Used it to be thought B. Did it used to be thought C. Was it used to being thought D. Does it used to be thought 参考答案:A 答案解析:It used to do句型的疑问句形式可以为Used it to do...或者Did it use to do...