VB.Net How to close random choosed form - vb.net

Question

I am making some kind of quiz. I have made randomizer for questions. So when one question(form) pops up and when I click the right answer new form pops up, where you have one label and button to continue. I have made that when I click continue button next question(form) pops up, but i want that the previous form closes too, but i dont know how to name it or what to do.
Dim rn As New Random
TextBox1.Text = rn.Next(1, 4)
If TextBox1.Text = 1 Then
Form4.Show()
Form4.Timer1.Start()
End If
If TextBox1.Text = 2 Then
Form7.Show()
Form7.Timer1.Start()
End If
If TextBox1.Text = 3 Then
Form8.Show()
Form8.Timer1.Start()
End If
If TextBox1.Text = 4 Then
Form12.Show()
Form12.Timer1.Start()
End If

Answer 1

Hand over a reference to the question to the result form. Then you can call the Close() method on the previous question before opening the next one.

Answer 2

How about a routine that closes all your forms before opening a new one.
This isn't the best way - as your telling the forms to close even if they weren't open.
But it will do what you are asking.
Here is an example:
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
Dim rn As New Random
Dim randomForm As UInteger = rn.Next(1, 3) 'Random Form Number
TextBox1.Text = randomForm 'Store the Random Number here
closeQuestionForms() 'Routine called before opening others
Select Case randomForm
Case 1
Form2.Show()
'Do something else here
Case 2
Form3.Show()
End Select
End Sub
Private Sub closeQuestionForms() 'Closes the forms
Form2.Close()
Form3.Close()
MessageBox.Show("Closed Question Forms")
End Sub
Again, There is probably a better way which other answers might show you. But this way should work fine.