a(1)=False

For i = 2 To 20

       a(i) = True

Next i

For i = 2 To 20

      If a(i) = True Then

        For j = 2 To 20 \ i

          a(i * j) = False

        Next j

      End If

Next i

t = 0

For i = 1 To 20

      If a(i) = True Then

        t = t + 1

      End If

Next i

经过该程序段运行后，变量t的值为（   ）

Dim a(1 To 5) As Integer

Dim f As Boolean

a(1) = 23: a(2) = 12: a(3) = 56: a(4) = 34: a(5) = 10

i = 1: f = True

Do While i <= 5 And f = True

  If a(i) = 56 Then f = False

  i = i + 1

Loop

Label1.Caption = i

DIM A（1991 TO 1998） AS INTEGER

FOR I=1 TO 8

   A(I)=I

PRINT A(I)；

       NEXT I

For i=1To n＼2   

    k=i

        If a(j) <a(k) Then k=j

    Next j

    If i<>k Then

        t=a(i)：a(i)=a(k)：a(k)=t

    End If

    If  Then

        t=a(j)：a(j)=a(j+1)：a(j+1)=t

      End If

    Next j

Next i

上述程序中方框处可选语句或表达式有：

①For j=i+1 To n-i+ 1    ②For j=i+1 To n-i

③a(j)<a(j+1) ④a(j)>a(j+1)

则(1)、(2)、(3)处语句依次是（  ）