问题：

[单选]

You are creating a Windows application for graphical image processing by using the .NET Framework 3.5. You create an image processing function and a delegate.You plan to invoke the image processing function by using the delegate.You need to ensure that the calling thread meets the following requirements： 
（1）It is not blocked when the delegate is running  
（2）It is notified when the delegate is complete
What should you do？（）

A . Call the Invoke method of the delegate.
B . Call the BeginInvoke and EndInvoke methods of the delegate in the calling thread.
C . Call the BeginInvoke method by specifying a callback method to be executed when the delegate is complete.Call the EndInvoke method in the callback method.
D . Call the BeginInvoke method by specifying a callback method to be executed when the delegate is complete.Call the EndInvoke method of the delegate in the calling thread.