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.) 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 use Microsoft .NET Framework 4 to create a Windows Forms client application. You write the following code segment. The application contains a form of type Form1 that contains a FormSettings object named frmSettings1. You need to maintain the users form size preference each time the user executes the application. Which code segment should you use? （）