Private Sub Command1_Click()

Dim s As Integer

Dim n As Integer

Dim i As Integer

n = Val(Text1.Text)

s = 1

For i = 2 To n

  s = s * i

Next i

Label1.Caption = Str(n) + "!=" + Str(s)

End Sub

Private Sub Text1_Change()

  Dim a, i As Integer

a= Val(Text1.Text)

  For i = 2 To 6 Step 2

    If a<= 15 Then a = a + i

  Next i

  Text1.Text = Str(a)

End Sub

若在文本框Text1中输入2，执行该程序段，For语句的循环次数为（  ）

For i = 1 To 3

 For j = 1 To 10

  If j Mod i = 0 Then a(j) = 1 - a(j)

 Next j

Next i

sum = 0

For i = 1 To 10

 sum = sum + a(i)

Next i

已知数组a的所有元素初值均为0，运行上述程序段后，变量sum的值是（  ）