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问题 单项选择题

以下关于元组叙述错误的是______。

A．关系是一个元数为K(K≥1)的元组的结合

B．关系中不允许出现相同的元组

C．元组中属性按一定次序排列

D．关系中不考虑元组之间的顺序

答案

参考答案：C

解析： 元组中属性是无序的，所以本题的答案为C。

句型转换

按要求对下列句子进行句型转换。

1. This is my sister. (变为复数句)

                                                                                                                           

2. He is twelve years old. (对划线部分提问)

                                                                                                                           

3. Danny can fly a kite. (改为一般疑问句)

                                                                                                                            

4. I have two chairs. (改为否定句)

                                                                                                                            

5. Li Ming and Jenny want to go shopping today. (对划线部分提问)

                                                                                                                            

6. It's 6:40 now. (对划线部分提问) 

                                                                                                                            

7. The book is under the desk. (对划线部分提问)

                                                                                                                            

8. May I take your picture? (作否定回答) 

                                                                                                                            

9. Walk quickly，please. (改为否定句)  

                                                                                                                             

10. Are you hungry? (作肯定回答)

                                                                                                                              
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多项选择题

急性血源性化脓性骨髓炎早期诊断依据是

A．起病急，全身感染中毒症状重

B．患部持续剧痛及深压痛，不愿活动患肢

C．局部分层穿刺抽出液检查有脓细胞或细菌

D．X线片可见骨破坏和骨增生

E．有死骨形成
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