问题
单项选择题
关系数据模型通常由3部分组成，它们是
A．数据结构，数据通信，关系操作
B．数据结构，数据操作，数据完整性约束
C．数据通信，数据操作，数据完整性约束
D．数据结构，数据通信，数据完整性约束
答案
参考答案：B
解析： 关系模型由关系数据结构、数据操作和数据完整性约束3大要素组成。
搜题请搜索小程序“爱下问搜题”
关系数据模型通常由3部分组成，它们是
A．数据结构，数据通信，关系操作
B．数据结构，数据操作，数据完整性约束
C．数据通信，数据操作，数据完整性约束
D．数据结构，数据通信，数据完整性约束
参考答案：B
解析： 关系模型由关系数据结构、数据操作和数据完整性约束3大要素组成。
FUN TIME
| 9 | 2 | 4 | 7 | 6 | 3 | 1 | 5 | 8 |
| 5 | 3 | 6 | 8 | 9 | 1 | 4 | 2 | 7 |
| X | 7 | 8 | 2 | 5 | 4 | 9 | 6 | 3 |
| 7 | 1 | 9 | 3 | 4 | 2 | 5 | 8 | 6 |
| 4 | 8 | 3 | 6 | 1 | 5 | 2 | 7 | 9 |
| 2 | 6 | 5 | 9 | 8 | 7 | 3 | 4 | 1 |
| 3 | 9 | 7 | 4 | 2 | Y | 6 | 1 | Z |
| 6 | 5 | 2 | 1 | 7 | 9 | 8 | 3 | 4 |
| 8 | 4 | 1 | 5 | 3 | 6 | 7 | 9 | 2 |
The rule of the puzzle is to fill in the grids (格子) so that every row, every line and every 3×3 box has the numbers 1 to 9. Here is a Sudoku. Please relax and enjoy. It’s fun!
根据以上杂志专栏内容，回答下列问题。
小题1:Who created Sudoku?
A．Howard Garnes.
B．Sudoku.
C．Kaji Maki.
D．Nikoli.小题2:Which is true about Kaji Maki according to the reading material?
A．He was the boss of Nissan Company.
B．He helped to make Sudoku popular in Japan.
C．He was the president of The Times.
D．He is an American.小题3:Which is NOT true about Sudoku?
A．Sudoku wasn’t invented in Japan.
B．It was The Times that first printed Sudoku in the newspaper.
C．Each grid has more than one number.
D．It became popular around the world in 2005.小题4:In the puzzle above, what should “X” be?
A．5.
B．4.
C．3.
D．1.小题5:What should “Z” be in the puzzle?
A．8.
B．5.
C．2.
D．4.