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【单选题】
女性月经周期中，月经来潮是由于血中的
A.
E2 浓度下降，P浓度升高
B.
E2 和P浓度均下降
C.
E2 浓度升高，P浓度下降
D.
LH 浓度显著升高而形成LH峰
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参考答案：
举一反三
【简答题】关系数据库的 规则规定:基本关系的主属性不能取空,关系数据库的 规则规定:一个基本关系的外码(对应于另一个基本关系的主码)取值取空值或者必须等于它所对应基本关系中的主码值。
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【单选题】一个基本关系中,主属性( )。
A.
可以有多个
B.
只有一个
C.
可以是零个
D.
以上都不是
查看完整题目与答案
【单选题】北京大学域名http://www.pku.edu.cn/中，edu代表的是( )。
A.
商业机构
B.
网络服务机构
C.
政府机构
D.
教育机构
查看完整题目与答案
【单选题】下列通用顶级域名中,表示网络服务机构的是【】
A.
.edu
B.
.net
C.
.org
D.
.int
查看完整题目与答案
【单选题】DNS顶级域名中表示网络服务机构的是（　 　　）。
A.
com
B.
edu
C.
gov
D.
net
查看完整题目与答案
【单选题】We may understand from the end of the passage that many foreign companies insist that ______.
A.
India should not give up opportunities to develop itself
B.
India has a great deal of potential to develop its economy
C.
there is still a lot of potential for foreign investment to enter India
D.
India as the world's largest democracy should have the responsibility to absorb foreign investment
查看完整题目与答案
【单选题】DNS顶级域名中表示网络服务机构的是（　 　　）。
A.
com
B.
edu
C.
org
D.
net
查看完整题目与答案
【多选题】若属性(或属性组)F是基本关系R的外码它与基本关系S的主码Ks相对应(基本关系R和S不一定是不同的关系),则对于R中每个元组在F上的值必须为:()
A.
取空值（F的每个属性值均为空值）
B.
等于R中某个元组的主码值
C.
等于S中某个元组的主码值
D.
无所谓
查看完整题目与答案
【单选题】Consider an accounting firm which hires workers to enter data into a computer program. Which of the following would be considered a short run decision?
A.
The firm would like to hire ten more workers for a weekend shift.
B.
The firm is considering an investment in additional computers.
C.
The firm would like to build its own facility.
D.
The firm might purchase new computer software that would require some new computer hardware as well as extensive training for workers.
查看完整题目与答案
【简答题】One of the biggest challenges facing students and their families is what career they should enter and what is the best path for them to take. I was talking to someone the other day who told me he firs...
查看完整题目与答案
相关题目：
【简答题】关系数据库的 规则规定:基本关系的主属性不能取空,关系数据库的 规则规定:一个基本关系的外码(对应于另一个基本关系的主码)取值取空值或者必须等于它所对应基本关系中的主码值。
查看完整题目与答案
【单选题】一个基本关系中,主属性( )。
A.
可以有多个
B.
只有一个
C.
可以是零个
D.
以上都不是
查看完整题目与答案
【单选题】北京大学域名http://www.pku.edu.cn/中，edu代表的是( )。
A.
商业机构
B.
网络服务机构
C.
政府机构
D.
教育机构
查看完整题目与答案
【单选题】下列通用顶级域名中,表示网络服务机构的是【】
A.
.edu
B.
.net
C.
.org
D.
.int
查看完整题目与答案
【单选题】DNS顶级域名中表示网络服务机构的是（　 　　）。
A.
com
B.
edu
C.
gov
D.
net
查看完整题目与答案
【单选题】We may understand from the end of the passage that many foreign companies insist that ______.
A.
India should not give up opportunities to develop itself
B.
India has a great deal of potential to develop its economy
C.
there is still a lot of potential for foreign investment to enter India
D.
India as the world's largest democracy should have the responsibility to absorb foreign investment
查看完整题目与答案
【单选题】DNS顶级域名中表示网络服务机构的是（　 　　）。
A.
com
B.
edu
C.
org
D.
net
查看完整题目与答案
【多选题】若属性(或属性组)F是基本关系R的外码它与基本关系S的主码Ks相对应(基本关系R和S不一定是不同的关系),则对于R中每个元组在F上的值必须为:()
A.
取空值（F的每个属性值均为空值）
B.
等于R中某个元组的主码值
C.
等于S中某个元组的主码值
D.
无所谓
查看完整题目与答案
【单选题】Consider an accounting firm which hires workers to enter data into a computer program. Which of the following would be considered a short run decision?
A.
The firm would like to hire ten more workers for a weekend shift.
B.
The firm is considering an investment in additional computers.
C.
The firm would like to build its own facility.
D.
The firm might purchase new computer software that would require some new computer hardware as well as extensive training for workers.
查看完整题目与答案
【简答题】One of the biggest challenges facing students and their families is what career they should enter and what is the best path for them to take. I was talking to someone the other day who told me he firs...
查看完整题目与答案
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