签定包车合同时，包车人应缴付定金。承运人违约时（）定金。A.不返还 B.双倍返还 C

改错。

( ) 1. His sister have got lots of toys.

                             A           B        C                            ________________________________

( ) 2. Xinjiang is in the east of China.

                             A        B   C                                    ________________________________

(     ) 3. I stayed there with my mother on a week last month.

                  A               B                    C                       _________________________________

(    )4. Last year he go to Dalian and swam in the sea.

                               A                         B    C                 ________________________________

机动车仪表板上（如图所示）亮时，提醒驾驶人安全带插头未插入锁扣。

Once in bed,I read for twenty minutes and then _______ the light.

A．turned out

B．turned over

C．turned on

D．turned up

以下( )模式必定符合4NF。

A) 关系R中只包含两个属性
B) 关系R中只包含三个属性
C) 关系R中都是主属性
D) 关系R中都是主属性，且没有非平凡函数依赖

在请求分页系统中，应从何处将所需页面调入内存？