问题
单项选择题
关系数据模型中表和表之间的数据联系是通过以下( )来实现的。
A．主码
B．指针
C．外码
D．链表
答案
参考答案：C
搜题请搜索小程序“爱下问搜题”
关系数据模型中表和表之间的数据联系是通过以下( )来实现的。
A．主码
B．指针
C．外码
D．链表
参考答案：C
| 完型填空。 |
| I am taking my family to Europe this year. My wife and I and our two 1 are going. My brother is a farmer. He decided to go with 2 . First he is going on his horseback from his farm to the 3 station. Then he is taking a bus to our house. From here, we are going 4 . We are going to go by train to New York, and then take a ship to Europe. When we arrive in 5 , we are going to rent a car and 6 wherever we want to go. Then we are going to return the 7 . We are planning to fly home. It took us a long time to decide our 8 . At first we wanted to 9 to Europe because it was faster. But my brother prefers to take a 10 trip. The children like that too. |
| ( )1. A. horses ( )2. A. us ( )3. A. train ( )4. A. together ( )5. A. Australia ( )6. A. walk ( )7. A. ship ( )8. A. place ( )9. A. go ( )10. A. bus | B. dogs B. them B. railway B. back B. Canada B. run B. horse B. time B. fly B. train | C. sisters C. him C. bus C. over C. Russia C. drive C. bike C. trip C. come C. boat | D. children D. me D. underground D. again D. Europe D. ride D. car D. w ay D. run D. plane |