单项选择题 You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You need to ensure that users can view content in a book-reading format that displays two pages at a time. Which control should you use?（）

单项选择题 You use Microsoft .NET Framework 4 to create a Windows Forms application. You write the following code segment. (Line numbers are included for reference only.) 01sealed class FormSettings : You need to ensure that the first time each user opens the application, a text field displays the following message: "Please enter your setting." Which code segment should you insert at line 03?（）

单项选择题 You upgrade a Windows Forms application to Microsoft .NET Framework 4. The application was developed by using a previous version of the .NET Framework. The application uses the Code Access Security (CAS) policy for file access. When the application is executed, you receive the following exception: "NotSupportedException: This method uses CAS policy, which has been obsoleted by the .NET Framework." You need to resolve the error. What should you do?（）