在上述图书管理数据库中，图书的主索引是总编号，读者的主索引是借书证号，借阅的主索引应该是[6] 。
参考答案：总编号+借书证号或借书证号+总编号
阅读理解。
Lucy and Lily are English girls. They are twins. They are studying Chinese in Beijing now. They are in Miss Gao's class. In their class, there are fifty-two students. There are twenty-eight boys and twenty-four girls.
Where are the twins? Look, they are sitting near the door of the classroom Lucy is wearing a red coat. Lily is wearing a yellow sweater. They are having a Chinese class. They like Chinese.
根据短文内容判断正（ T）误 （F）。
( )1. The two girls are twins. They are in a school of China.
( )2. Lucy and Lily are in the same class.
( )3. Lucy is in a yellow sweater.
( )4. Now they are studying Chinese in the classroom
( )5. There are twenty-eight girls in their class.
大于3.51而小于3.59的数共有（ ）个．
A．7
B．8
C．9
D．无数
