s=0

For i=1  to  5   step  -2

   s=s+i

Next i

执行上述代码后，下列说法正确的是（  ）

  If (a Mod 3 = 0) Or (b Mod 3 = 0) Then

 c = a * b

  Else

  c = a + b

  End If

执行后变量c的值为（   ）

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（  ）

Dim a(1 To 10) As Integer, f(1 To 20) As Boolean

    'f数组各元素的初值设为False，代码略

    For i = 1 To 10

       t =int(rnd()*20+1)

       If Not f(t) Then

          a(i) = t:      ⑴     

          For j = i To 2 Step -1

             If    ⑵    Then

                tmp = a(j): a(j) = a(j - 1): a(j - 1) = tmp

             End If

          Next j

       Else

               ⑶    

       End If

    Next i

上述程序中3处下划线应填入的程序代码是（  ）