当前流行的关系数据库管理系统一般都会提供一系列安全措施。以下不属于数据库安全措施的是
A．用户标识与鉴别
B．存取控制
C．视图和触发器
D．并发控制
参考答案：D
解析：当前流行的关系数据库管理系统一般都提供如下的安伞措施：用户标识与鉴别（Identification and Authetication)、存取控制、审计（audit)、定义数据库对象，如视图、存储过程、触发器等。数据库数据以系统内码表示，对要数据加密。
As Christmas drew near, Ursula was faced with just that problem. She had come to live in an American home and learn English. 31 , she would mind the children and do anything she was asked. One of her tasks was to keep track of arriving Christmas presents. Ursula did this faithfully, but she became increasingly worried. What could she buy for her 32 with the little money she had that would compare with the gifts she was recording daily? 33 , even without any of the gifts , her employer seems to have everything. Ursula 34 long and hard. On Christmas Eve, she went to a store. She moved slowly through crowds of shoppers, 35 things in her mind. Finally she bought a baby dress. She immediately called a taxi. “Excuse me, please, can you help me find a poor family with a baby?” “A poor family?” said the 36 driver. “Yes, a very poor family.” Ursula told the man what she was trying to do. He listened in silence, and then said, “I know a family who needs just about everything.” When they reached a building, the driver said, “They live on the third floor.” Ursula shook her head, “Would you take this dress to them and tell them it’s from someone …someone who has everything.” Early the next day, Ursula 37 everyone for the presents she received. Then, she began to 38 why there seemed to be none from her. She told about what she did the night before. When she finished, there was a long 39 . “You see,” she added, “I try to do a kindness in your 40 . And this is my Christmas present to you.”
|