What is displayed when the button is clicked?

Private Sub btnDisplay_Click(...) Handles btnDisplay.Click
Dim a, b as String
Dim x as Integer
a = "How now brown cow."
b = "brown"
x = FindIt(a, b)
txtBox.Text = CStr(x)
End Sub
Function FindIt(ByVal z1 as String, ByVal z2 as String) As Integer
Dim x as Integer
x = z1.IndexOf(z2)
End Function
"How now"
A. 8
B. 0
C. An error
D. None of the above

Ans: D