题目

如果两个质数的差为2，则这两个质数称为孪生质数对；编写VB程序，实现如下功能：单击“显示孪生质数对”按钮Command1，在列表框list1中显示100以内的所有孪生质数对(运行效果如图所示)。 实现上述功能的VB代码如下, 但划线处代码有错，请改正。Dim a(1 To 50) As IntegerPrivate Sub Command1_Click()Dim i As Integerk = 0: i = 3Do While i <= 100   If  ① prime(i)   Then      ‘⑴      k = k + 1      a(k) = i   End If      i = i + 2LoopFor i = 2 To k   If   ②a(i) = a(i +1)+2   Then   ‘⑵      List1.AddItem Str(a(i - 1)) + "和" + Str(a(i))   End IfNext iEnd SubFunction prime(x As Integer) As Booleanprime = FalseFor i = 2 To Int(Sqr(x))   If  x Mod i = 0  Then      prime = True      Exit For   End IfNext iEnd Function①   ②   答案：【1】prime(i)=false【2】a(i) = a(i -1)+2 or a(i) +2 = a(i -1)

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