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.