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【简答题】
解释下列术语的含义:  (1)主键  (2)候选键   (3)关系模式
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参考答案:
举一反三
【单选题】How was your trip to Paris?
A.
Take care.
B.
It’s great.
C.
My pleasure.
D.
This way please.
【单选题】严格意义上来讲,下列哪类人群最好不要使用应急医疗箱
A.
乘务人员
B.
在场的医生
C.
在场的护士
D.
机长
【单选题】Sam had a trip to Paris last month. Which of the following is the picture he took there?
A.
B.
C.
【单选题】—Visitors need to know all the travel routes to Paris, ______? —Sure. But The trip has not arranged.
A.
do they
B.
need they
C.
don't they
D.
needn't they
【单选题】对于二极管,以下说法不正确的是 。
A.
二极管加正向电压时,二极管就导通
B.
二极管的反向饱和电流的大小受温度影响大
C.
二极管的正向导通压降,硅管比锗管高
D.
同样外部条件下, 硅管的 反向饱和电流比锗管小
【单选题】—Visitors need to know all the travel routes to Paris, ______? —Sure. But The trip has not arranged.
A.
do they        
B.
need they
C.
don't they      D needn't they
【简答题】____________ (所一切都考虑过后), the trip to Paris has to be called off.
【单选题】二极管 ( PN结 ) 正向导通的条件是外加电压( )。
A.
>0
B.
>死区电压
C.
>击穿电压
【判断题】水稻未加倍的花粉植株是单倍体,其实也是一倍体。
A.
正确
B.
错误
【单选题】The teacher _____ some old friends on his vacation trip to Paris. [     ]
A.
dropped by
B.
dropped in
C.
droped by
D.
droped in
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