单项选择题 You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You create a game where a ball drops from the top to the bottom of a window. You plan to create a single animation for the game. You need to ensure that the animation shows the ball bounce. What should you do?（）

单项选择题 You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. The application contains a form named frmMain that contains a button named btnSave. You create a ProgressBar control named saveProgress. Initially, saveProgress is not displayed on frmMain. When a user clicks btnSave, you have the following requirements: saveProgress is slightly visible after 0.2 seconds saveProgress is fully visible after 1 second You need to declare the corresponding storyboard. You write the following code fragment. (Line numbers are included for reference only.) Which code fragment should you insert at line 02 to complete the declaration?（）

单项选择题 You use Microsoft .NET Framework 4 to create a Windows Presentation Foundation (WPF) application. You create a window named ManageOrders that contains a Button control named showOtherSide. You add an animation named FlipSides as a resource of ManageOrders. You need to ensure that the following requirements are met: FlipSides runs each time a user clicks showOtherSide. FlipSides runs only when a user clicks showOtherSide. What should you do?（）