下面程序产生 20 个互不相同的两位随机整数,以每行 4 个的形式输出到窗体上。请完善 程序。 Option Base l Private Sub Commandl_Click() Dim i As Integer,j As Integer,x As Integer,flag As Integer Dim a(20) As Integer,k As Integer Randomize For i=1 T0 20 Do x=Int( Rnd *90) +10 flag=0 For j=1 To i-1 If _______ Then fiag=1 End If ____________________ Next j Loop While _________ Print a(i) ; k =k+1 If k mod 4=0 Then_____________ Next i End Sub