单项选择题

数据库的三级模式结构由外模式、模式和内模式组成，它适合于哪个（些）类型的数据库？（） Ⅰ.关系型数据库 Ⅱ.层次型数据库 Ⅲ.网状型数据库

A．只有Ⅰ
B．Ⅰ和Ⅱ
C．Ⅱ和Ⅲ
D．都适合

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单项选择题

Are based on the following Pascal code. FOR i:=1 TO n -1 do BEGIN k:=i: FOR j:=i+1 TO n DO IF A[j] THEN k:=j: IF k<>i THEN BEGIN X:=A[k]; A[k]:=A[i]; A[i]:=x END END; <---> Suppose elements in array A are already sorted ascending order of their values when the code begins to run, then execution time of the code will be（）

A．O(log2n)
B．O(n)
C．O(nlog2n)
D．O(n2)

单项选择题

Prototype method is one of the software engineering methods frequently used, which of the following item is the necessary condition for implementing prototype method （） Ⅰ．Can acquire the user requirement quickly Ⅱ．Have the tools for building software fast Ⅲ．Have a certain accumulation of prototype systems

A．Ⅰ only
B．Ⅰand Ⅱ
C．Ⅱ and Ⅲ
D．all

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