设选课表的结构为：(学号、课程号、成绩)，其中学号+课程号为主键。要从选课表中统计每个学生选修的课程门数，应使用的SELECT语句是______。
A. SELECT COUNT(*) FROM 选课表
B. SELECT COUNT(*) FROM 选课表 GROUP BY学号
C. SELECT DISTINCT COUNT(*) FROM 选课表
D. SELECT DISTINCT COUNT(*) FROM 选课表 GROUP BY学号
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According to the speaker, David thinks the two different approaches
A. are working in parallel.
B. are working in harmony.
C. are working in discord.
D. are working in collaboration.
关系型数据库中，实现表与表之间的联系是通过______。
A. 实体完整性规则
B. 参照完整性规则
C. 用户自定义的完整性
D. 值域
等高式大放脚的砌法为二皮一收，每次收进宽度为（）砖长。
A. 1/3
B. 1/4
C. 1/5
D. 1/6
The congress, by a two-third vote in each house, may ______ an amendment to the Constitution.
A. start
B. initiate
C. begin
D. propose
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