You use Microsoft .NET Framework 4 to create a Windows Presentation Framework (WPF) application. You plan to create a custom control that contains four text input fields. Each of the text input fields within the control will contain a label. You need to ensure that the text input fields within the control can be validated by using a regular expression validator. Which class should you inherit from?（）
- A TextBox
- B TextElement
- C UIElement
- D UserControl