Identify the error in the following code:

Private Sub btnCalculate_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles btnCalculate.Click
' Declare some variables
Dim sngNumber1 As Single
Dim sngNumber2 As Single
Dim sngSum As Single

' Get the two numbers
sngNumber1 = txtNumber1.Text
sngNumber2 = txtNumber2.Text
' Calculate their sngSum... is the next line working?
sngSum = sngNumber1 + sngNumber2
' Display the result
lblSum.Text = sngSum.ToString
End Sub

a. A local variable is misplaced.
b. A conversion function such as CSng was not used.
c. The variable name sngNumberl was misspelled.
d. The variable sngSum was declared as the wrong data type.

b. A conversion function such as CSng was not used.