You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You write the following code fragment. < StackPanel…

You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You write the following code fragment. < StackPanel TextBox.PreviewTextInput="StackPanel_PreviewTextInput" > < TextBox Name="TxtBoxA"/> < TextBox Naroe="TxtBoxB"/> < TextBox Name="TxtBoxC"/> < /StackPanel> You create an event handler named StackPanel_PreviewTextInput. You also have a collection of strings named Keywords. You need to ensure that TxtBoxA and TxtBoxB do not contain any of the strings in the Keywords collections. Which code segment should you use?