a(1) = 2

For i = 2 To 3

  a(i) = a(i - 1) - Int(Rnd() * 2)

  If i Mod 2 = 1 Then

    a(i) = a(i) + 1

  Else

    a(i) = a(i) - 1

  End If

Next i

执行程序后，a(2)和a(3)的值不可能的是（   ）

实现以上功能的VB程序如下,在横处填入合适的代码。

Dim a(1 To 20) As Integer     ‘存储区间的左端点数值

Dim b(1 To 20) As Integer     ‘存储区间的右端点数值

Private Sub Form_Load()

‘将区间左端点存入数组a,区间右端点存入数组b,并在列表框List1显示,代码略

End Sub

Private Sub Command1_Click()

Dim i As Integer, j As Integer

Dim curL As Integer, curR As Integer

For i=1 To n-1

 For j=1 To n-i

  If{#blank#}1{#/blank#}Then

   t=a(j): a(j)=a(j+1): a(j+1)=t

   t=b(j): b(j)=b(j+1): b(j+1)=t

  End If

 Next j

Next i

curL=a(1): curR=b(1)

For i=2 To n

 If{#blank#}2{#/blank#}Then

  If curR < b(i) Then{#blank#}3{#/blank#}

 Else

  List2.AddItem“["+Str(curL)+Str(curR)+"]”

  curL=a(i): curR=b(i)

 End If

Next i

List2. AddItem “[”+Str(curL)+Str(curR)+“]”

End Sub

Dim a(1 To 5) As Integer

For i = 1 To 5

    a(i) = Int(Rnd * 30 + 10)

    t = t + a(i) \ 10

Next i

For j = 1 To t \ 3

    If j Mod 2 = 1 Then a(j) = a(j) + 1 Else a(j) = a(j) - 1

Next j

运行程序后，数组a各个元素的值，不可能的是（  ）

For i = 1 To 6

a(i) = Int(Rnd * 10) + 1

Next i

For i = 2 To 6

If i Mod 2 = 0 And a(i)>a(i-1) Then

t=a(i)：a(i)=a(i-1)：a(i-1)=t

Else

a(i)=a(i)-1

End If

Next i

执行程序后，数组元素a(1)到a(6)的值可能是(  )