单项选择题 You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. The application uses the drag-and-drop functionality. You need to ensure that the drag-and-drop operation is stopped when a user moves the cursor outside the boundaries of the application form. Which enumeration member should you use?（）

多项选择题 You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. The application uses the background worker process (BWP). When the user clicks a button, the background worker executes a method named DoCalculations asynchronously. You need to implement a progress bar on the user interface (UI) that informs the user of the progress of DoCalculations. Which two actions should you perform?（）

单项选择题 You use Microsoft .NET Framework 4 to create an application. The application performs resource-intensive calculations that consist of multiple layers of nested looping. The application will be deployed to servers that contain varying hardware configurations. You need to ensure that the application utilizes CPU resources on the server in the most efficient manner. You want to achieve this goal by using the minimum amount of code. What should you do?（）