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【单选题】
查询选修了课程号为“C1”的学生的姓名和年龄，若用下列SQL的SELECT语句表达 时，错误的是（ ）。A.
SELECT SNAME，AGE FROM S WHERE S ．S#=（SELECT SC．S# FROM SC WHERE C．C#=’C 1’）
C.
SELECT SNAME，AGE FROM S，SC WHERE S．S#=SC．S# AND SC．C#=’C 1’ C．SELECT SNAME，AGE FROM S，SC WHERE S．S#=SC．S# AND SC．C#=’CI’ ORDER B Y S．S#
D.
SELECT SNAME，AGE FROM S WHERE S．S#=（SELECT SC．S# FROM SC WHERE SC．C#=’C 1’）
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【单选题】在磁盘和磁带这两种磁介质存储器中,存取时间与存储单元的物理位置有关,按存储方式分, 。
A.
二者都是顺序存取
B.
二者都是直接存取
C.
磁盘是直接存取，磁带是顺序存取
D.
磁带是直接存取，磁盘是顺序存取
【单选题】Which of the following is not held constant when moving along a product's demand curve?
A.
The price of the product itself.
B.
The expected price of the product in the near future.
C.
Income.
D.
Prices of complementary goods.
E.
Prices of substitutes.
【单选题】When an economist refers to a product as a "normal good," it implies that
A.
when incomes rise, demand for that product will fall.
B.
when incomes decline, demand for that product will fall.
C.
there are many good substitutes for the product.
D.
the product is of poor quality.
【单选题】在磁盘和磁带这两种磁介质存储器中,存取时间与存储单元的物理位置有关,按存储方式分为( )。
A.
二者都是顺序存放
B.
二者都是直接存取
C.
.磁盘是直接存取,磁带式顺序存取
D.
磁带是直接存取,磁盘是顺序存取
【单选题】在磁盘和磁带这两种磁介质存储器中,存取时间与存储单元的物理位置有关,按存储方式分( )。
A.
二者都是顺序存取
B.
二者都是直接存取
C.
磁盘是直接存取，磁带是顺序存取
D.
磁带是直接存储，磁盘是顺序存取
【单选题】When 'product differentiation' is adopted, the product is usually______.
A.
advertised as something different from similar products
B.
good either for your health or for the environment
C.
very profitable for the company
D.
environmentally friendly
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