设有关系SC(SNO，CNO，GRADＥ)，主码是(SNO，CNＯ)。遵照实体完整性
题型：单项选择题
问题：
设有关系SC(SNO，CNO，GRADＥ)，主码是(SNO，CNＯ)。遵照实体完整性规则
A) 只有SNO不能取空值 B) 只有CNO不能取空值
C) 只有GRADE不能取空值 D) SNO与CNO都不能取空值
题型：单项选择题
阅读理解。
Mary is a girl. She is a middle school student. She is in Class Three, Grade Two.
There is a big picture in Mary's bedroom It's the picture of the family. Mary's mother is a teacher of
Chinese. There is a nice pen in the pocket of her white coat. Mary's father is a worker. There is a big
red flower on his black coat. He is at work from Tuesday to Sunday. Mary's brother is near her
mother. He is a middle school student, too. He is fourteen. He is in Grade Three.
Mary and her brother like books. They like school. They work hard). They are good students.
1. This is a picture of _____.
A. Mary
B. Mary'
s family
C. Mary's father
D. a middle school
2. Mary is _____.
A. fourteen
B. eleven
C. thirteen
D. fifteen
3. Mary
's father and mother are_____.
A. worker and teacher
B. worker and nurse
C. teacher and doctor
D. doctor and nurse
4. There is a red flower on _____ coat .
A. Mary's
B. Mary's brother's
C. Mary's brother's
D. Mary's father's
5. _____ on Monday.
A. They four are all at home
B. Mary and her brother go to school
C. Only Mary's father is at home
D. Mary's mother and father are not at work