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?（）

A. Modify the Value property of the progress bar in DoCalculations.
B. Modify the Value property of the progress bar in the ProgressChanged event handler of the background worker.
C. Modify the Value property of the progress bar in the RunWorkerCompleted event handler of the background worker.
D. Call the ReportProgress method of the background worker in DoCalculations.
E. Call the ReportProgress method of the background worker in the DoWork event handler of the background worker.